Benzenesulfonic acid, 4-C10-13-sec-alkyl derivs., compds. with ethanolamine

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1967

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Reason / purpose for cross-reference:

reference to same study

Objective of study:

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

The absorption, distribution, metabolism and elimination of LAS (radioactively labeled with 35S) were studied in male Charles River rats. LAS was administered orally as an aqueous solution.

GLP compliance:

no

Radiolabelling:

yes

Remarks:

(radioactively labeled with 35S)

Species:

rat

Strain:

other: Charles River albino

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 150-200 g
- Housing: The animals were housed in individual cages which permitted the separate collection of urine and feces.
- Diet: ad libitum
- Water: ad libitum

No further details on test animals and environmental conditions were provided in the source.

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Male rats (150-200 g) were fasted for 16 hours and given orally an aqueous solution containing LA35S. The dose was given in 1.0 mL volume. The urine was collected under toluene, removed daily, and refrigerated until it could be examined. The feces were removed each day and allowed to dry at room temperature. At the termination of the study, the animals were killed, and selected organs and tissues were taken for radioassay.

Measurements:
The route of absorption was determined by oral feeding of 40 mg of LAS to thoracic duct-cannulated rats. The lymph was collected from each animal in a single 42-hour fraction.


- The ability of the rat to absorb these surfactants was determined in bile duct-ligated rats. Each rat received orally 1.2 mg of either labeled compound. The urine and feces of each animal were collected for 90 hours after dosing.

-The enterohepatic circulation of the surfactant was quantified by oral feeding of 1.2 mg of LAS to bile duct-cannulated rats and to rats prepared in a manner similar to the dual rat study described by Boquet and Fromageot. A cannula was inserted into the proximal end of the bile duct of Rat A and into the distal end of the bile duct in Rat B such that the bile from Rat A could flow through the cannula into the bile duct, and finally into the intestine of Rat B. A second cannula was inserted into the proximal end of the bile duct of Rat B so that is bile could be collected. LA35S was fed orally to Rat A. Urine and feces of Rats A and B and bile of Rat B were collected for 90 hours after dosing.

- The excretion was measured after oral administration of 1.2 mg of radiolabeled LAS to bile duct-ligated rats. In another set of animals, LAS was also determined after single dose via stomach tube of 0.6, 1.2, 8.0 and 40.0 mg and excretion was estimated over a 3- day period.

Duration and frequency of treatment / exposure:

Excretion and distribution studies: Single oral dose of 0.6, 1.2, 8 or 40 mg
Absorption, enterohepatic circulation and excretion studies: Single oral dose of 1.2 mg
Route of absorption study: Single oral dose of 40 mg

Remarks:

0.6, 1.2, 8.0 and 40.0 mg for the excretion test, 1.2 mg/rat for the absorption and enterohepatic circulation tests, 40 mg for route of absorption study

No. of animals per sex per dose / concentration:

Excretion and distribution studies: Average of 5 animals for 0.6 and 1.2 mg dose levels and average of 3 animals for 8.0 and 4.0 mg dose levels
Route of absorption study: Six male rats
Enterohepatic circulation study: Three bile duct-cannulated rats connected to dual rat (total 6 rats)

Control animals:

no

Positive control reference chemical:

No positive control was included in the study.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, feces, bile and lymph
- Time and frequency of sampling:
- For route of absorption study: The lymph was collected from each animal in a single 42-hour fraction
- For evaluation of absorption of test substance: Urine and feces were collected for 90 hours after dosing.
- For evaluation of disposition: Urine and feces were removed daily.
- For quantification of enterohepatic circulation of test substance: Urine, bile and feces were collected for 90 hours after dosing.
- For evaluation of excretion: Urine was collected daily

METHOD OF ANALYSIS FOR TISSUES AND BODY FLUIDS: Urine, lymph, and bile were each assayed directly by liquid scintillation counting while the feces and tissues were wet ashed with HNOJ/HC104 followed by direct counting of an aliquot of the solution.

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: Urine and feces
- Time and frequency of sampling: Daily
- From how many animals: The urine from rats that were fed LAS was pooled.
- Method type(s) for identification: The column chromatography, infrared, nuclear magnetic resonance (NMR), and mass spectra of the metabolites isolated from the urine of rats were obtained and analysed.
- Limits of detection and quantification: not specified

Statistics:

No details were provided

Type:

absorption

Results:

80-90% of the administered dose was readily absorbed from the gastrointestinal tract.

Type:

metabolism

Results:

60-65 % of the absorbed dose was excreted in urine as a mixture of two polar metabolites i.e.sulfophenyl butanoic and sulfophenyl pentatonic acid.

Type:

excretion

Results:

LAS was primarily excreted in the urine.

Details on absorption:

The compound was readily absorbed from the gastrointestinal tract (80-90% of the dose).

Route of absorption: There was 1.6 % of the LAS detected in the lymph of the animals during the 42-hour collection period. LAS appeared to be absorbed from the gastrointestinal tract and transported by other than the lymphatic system, probably by way of portal venous blood.

Details on distribution in tissues:

Primarily excreted in the urine.

Details on excretion:

Most of the absorbed 35S was eliminated within 72 hours and 60-65% of the absorbed dose was eliminated in the urine as a mixture of two polar metabolites i.e.sulfophenyl butanoic and sulfophenyl pentatonic acid. These compounds were probably formed from LAS by ω-oxidation followed by catabolism through a ß-oxidation mechanism to form the metabolites that were excreted in the urine. The polar nature of metabolites resisted reabsorption from the kidney tubule and as the result were excreted primarily in the urine.35% of the absorbed 35S was excreted in the bile and was reabsorbed completely from the gastrointestinal tract. Very little was found in the lymph, so transport of LAS is probably by way of portal venous blood.
Chemical nature of 35S in the urine of rats fed LAS: The 35S in the urine was not precipitated by ethanol along with added carrier Na2SO4. In addition, it was not extracted from the urine along with the added carrier LAS when the assay of cationic-SO3 was used. The 35S was thus assumed to be present in the urine as a metabolite of LAS. At the end of the 3 days, no 35S residue (<1% of the dose) could be detected in the carcasses of the rats that received the 40 mg dose of either surfactant. No explanation could be found for the unusually low recovery of 3% in animal.

Metabolites identified:

yes

Details on metabolites:

Urine - sulfophenyl butanoic and sulfophenyl pentatonic acid. These metabolites were sufficiently polar to avoid being reabsorbed from the kidney tubules. Although the metabolites in the bile were not identified, it was shown that no unchanged LAS was eliminated via this pathway.

Table 1: Distribution of LA35S in urine and feces after administration of single dose of various quantities by stomach tube (Michael, 1968)

Quantities administered in mg	Percentage of dose excreted
	Day	Urine	Feces	Total
0.6^a	1	31.6	36.6	68.2
	2	7.8	18.1	25.9
	3	0.8	1.4	2.2
	Total	40.2	56.1	96.3
1.2^a	1	53.7	22.5	76.2
	2	3.3	15.5	18.8
	3	0.7	0.9	1.6
	Total	57.7	38.9	96.6
8.0^b	1	38	37.4	75.4
	2	1.3	2	3.3
	3	0.9	1.7	2.6
	Total	40.2	41.1	81.3
40.0^b	1	38.2	31	69.2
	2	2.7	11.9	14.6
	3	0.8	0.6	1.4
	Total	41.7	43.5	85.2

a: Average of 3 animals

b: Average of 5 animals

Table 2: Disposition of 3% in bile duct ligated rats 90 hours after a single dose of LAS (Michael, 1968).

	Percentage of recovered 35S activity
Urine	89
Feces	11
Total recovery of 35S	83

Conclusions:

Based on the results, C10-13 LAS is readily absorbed by the gastrointestinal tract and rapidly excreted with its metabolites, primarily in the urine.

Executive summary:

The purpose of the study was to determine the absorption, distribution and metabolic fate of test substance, C10-13 LAS in rats.

 

Charles river male rats (150-200 g) were used in this study. The rats were housed in individual cages which permitted the separate collection of urine and feces. For the determination of disposition profile of chemical, rats were fasted for 16 hours and given orally an aqueous solution containing LA35S. The dose was given in 1.0 mL volume. The urine and feces were collected daily for examination. At the termination of the study, the animals were killed, and selected organs and tissues were taken for radioassay.

 

The absorption, route of absorption and enterohepatic circulation of test substance were also quantified in the study. The route of absorption was determined by oral feeding of 40 mg of LAS to thoracic duct-cannulated rats. The lymph was collected from each animal in a single 42-hour fraction. For absorption study, each rat received orally 1.2 mg of test substance. The urine and feces of each animal were collected for 90 hours after dosing for analysis.

 

The enterohepatic circulation of the surfactant was quantified by using a dual rat study. In this, Rat A of one pair received 1.2 mg of LAS by stomach tube, while Rat A of second pair received another chemical. The 35S containing compounds from LA35S that were excreted in bile of Rat A and transferred by cannula to Rat B were completely absorbed from the gastrointestinal tract of Rat B, and nearly two-thirds of this activity was excreted in the bile of Rat B.

 

For the excretion study, the cumulative excretion of LA35S, at dose levels 0.6, 1.2, 8.0 and 40.0 mg over a 3- day period following a single administration is determined.

 

Urine and feces samples were also analyzed for the identification of metabolites. Various analytical techniques like column chromatography, infrared, nuclear magnetic resonance (NMR), and mass spectra were used for the determination of metabolites.

 

The results revealed 80-90% of the administered dose was readily absorbed from the gastrointestinal tract and excreted primarily through urine. Of the absorbed LA35S, 60-65 % was excreted in the urine as a mixture of sulfo - phenyl butanoic and sulfophenyl pentanoic acids. 35% of the absorbed 35S was excreted in the bile and was reabsorbed completely from the gastrointestinal tract. Very little was found in the lymph, so transport of LAS is probably by way of portal venous blood.

 

Based on the above, LAS was readily absorbed by the gastrointestinal tract, rapidly metabolized and excreted in the urine.

 

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

metabolism

Qualifier:

no guideline followed

Principles of method if other than guideline:

The disposition of radioactivity was studied in single and repeated oral doses of [14C] LAS to rhesus monkeys.

GLP compliance:

not specified

Radiolabelling:

yes

Remarks:

([14C] LAS)

Species:

monkey

Strain:

other: Macaca mulatta

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 5 kg average body weight
- Age at study initiation: Adult rhesus monkeys
- Housing: During the excretion studies, animals were housed in stainless steel metabolism cages which allowed separate collection of urine and feces.

Route of administration:

other: oral or subcutaneous

Vehicle:

water

Details on exposure:

Oral study: For excretion studies, single oral doses (14C-LAS of 30 mg/kg bw at 25 µCi) were administered by oral intubation as a solution in water. For the plasma level studies, the same animals were administered single oral doses (14C-LAS of 150 mg/kg bw at 26 µCi and 300 mg/kg bw at 28 µCi) at intervals of 2 -3 weeks. About 2 -3 weeks after the last single dose each animal received 7 consecutive daily oral doses of 14C-LAS (30 mg/kg bw/day at 28 µCi/day) in water (6 mL). Blood samples were taken, and animals were sacrificed at a different time after the last dose.

Subcutaneous study: For excretion studies, single doses (14C-LAS of 1 mg/kg bw at 16-40 µCi), as a solution in water, were administered by injection into the subcutaneous tissue between the shoulder blades. Similarly, for the plasma level tests, the same animals received subcutaneous doses of 0.5 and 0.1 mg/kg bw (8-22 and 2-5 µCi, respectively) at intervals of 2-3 weeks. About 2-3 weeks after the last single dose the animals received 7 consecutive daily subcutaneous doses of 1 mg/kg bw/day (about 24 µCi/day) in water. Blood samples were taken in both cases.

Excretion studies: After dose administration, urine was collected for 0-8 hours and 8-24 hours and thereafter at 24-hours intervals for another 4 days. Feces were collected at 24-hours intervals for 5 days. The cage interiors were washed with water at 24-hours intervals and the washings retained. Cage debris was collected separately at 24-hours intervals. Blood samples (3 mL) were withdrawn from the femoral vein into heparinised tubes at 30, 48, 72 and 96 hous after dosing. Cells were separated by centrifugation and the concentrations of radioactivity measured in the plasma.

Plasma studies
During the studies after single doses, blood samples (3 mL) were withdrawn before dosing and at 0.5, 1, 2, 4, 6, 7.5 and 24 hour and then at 24-hour intervals after dosing until concentrations of radioactivity in plasma were below the limit of detection. During repeated administration, blood samples were withdrawn at predose and at 0.5, 1, 2, 4, 6 and 7.5 hours after the first dose and immediately before administration of the following 6 doses. After the seventh and last dose, blood samples were taken at different times until sacrifice for the measurement of plasma concentrations. Single animals from each group were sacrificed at 2, 4, 24 and 48 h, by injection of sodium pentobarbitone (600 mg). The liver, kidneys, brain, spinal cord, pituitary, thyroid, eyes, lungs, gonads, heart, adrenals, pancreas, spleen, stomach, small and large intestine, omentum, mesentery, and samples of adipose tissue and muscle were removed. All samples were stored at -20°C until taken for analysis.

Duration and frequency of treatment / exposure:

Duration and frequency of treatment / exposure
Oral study:
i) Single dose of 30 mg/kg bw (at 25 µCi) for the excretion study
ii) Single dose of 150 mg/kg bw (26 µCi) and 300 mg/kg bw (28 µCi) for the plasma level studies
iii) Repeated dose of 30 mg/kg bw/day (28 µCi/day) for 7 days

Subcutaneous study:
i) Single dose of 1 mg/kg bw (at 16-40 µCi) for the excretion study
ii) Single dose of 0.5 mg/kg bw (8-22 µCi) and 0.1 mg/kg bw (2-5 µCi) for the plasma level studies
iii) Repeated dose of 1 mg/kg bw/day (24 µCi/day) for 7 days

Remarks:

single or repeated oral (30, 150 or 300 mg/kg bw) or subcutaneous (0.1, 0.5 or 1 mg/kg bw) doses of 14C-LAS

No. of animals per sex per dose / concentration:

2 males and 2 females

Control animals:

not specified

Positive control reference chemical:

No positive controls were used.

Details on dosing and sampling:

Blood samples were collected for the excretion and plasma studies.
Details on dosing and sampling
TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, feces, blood, plasma, bile and lymph
- Time and frequency of sampling: see exposure section

METABOLITE CHARACTERISATION STUDIES: Not examined Details on Radioactivity
Measurement of radioactivity in organs with a total weight of less than 1.0 g was carried out after direct combustion of the whole organ. Measurement of radioactivity in fat, muscle and spinal cord was carried out after direct combustion of duplicate samples of these tissues. Radioactivity was measured in a Liquid Scintillation Analyser (Philips N.V., The Netherlands) using automatic external standard quench correction, and was counted at efficiencies greater than 80%. Radioactivity was measured where possible in duplicate portions of each sample, and the measurements were rejected if they were not within ± 5% of the mean count.

Measurements of radioactive components in urine
Aliquots of urine were partially purified by high performance liquid chromatography using a Waters high pressure liquid chromatograph (Waters Associates Inc., Milford, U.S.A.} and a 10 µm ODS Spherisorb silica column 250 mm X 4 mm i.d. (Phase Separations Ltd., Queensferry, U.K.). Radioactive components on TLC plates were detected by autoradiography using Kodak Kodirex X-ray film.

Type:

distribution

Results:

Oral study: No specific accumulation or localisation of LAS and/or its metabolites in any of the analysed tissues. Sub-cutaneous study: Apart from the gastrointestinal tract, no accumulation of test substance apart from the gastrointestinal tract

Type:

excretion

Results:

In single 30 mg/kg bw oral doses or single 1 mg/kg bw subcutaneous doses, means of 71% and 64% respectively, were excreted in the urine and only 23% and 11% respectively in the feces.

Details on distribution in tissues:

When 14C-LAS was injected into the skin, most of the radioactivity remained at the site of injection.
No localization of radioactivity in any tissue occurred.

Plasma concentrations after oral doses: After single oral doses of [14C] LAS at a nominal dose level of 150 mg/kg bw concentrations declined during the period 6-24 hours with a mean half-life of about 6.5 hours and were below the limit of detection (<1.0 µg/mL) at 48 hours. At nominal dose level of 300 mg/kg bw, plasma concentrations declined during 6-24 hours with a mean half-life of about 5.5 hours. After the first of 7 consecutive daily oral doses of 30 mg/kg bw, plasma levels declined to 1.8 µg/mL at 24 hours with a mean elimination half-life of about 5 hours. After the seventh and final dose, mean plasma concentrations declined until 24 hours with a mean half-life of about 6 hours.

Tissue distribution after repeated oral doses:
At 2 hours, there were high concentrations in the stomach, which subsequently declined, although concentrations in the intestinal tract were highest in the animal sacrificed at 24 hours (255 µg/g). At 2 hours, concentrations were also high in liver (64.8 µg/g), kidneys (135.6 µg/g), lungs (19.8 µg/g), pancreas (17.7 µg/g), adrenals (20.6 µg/g) and pituitary (17.0 µg/g). At 4 hours, concentrations in these tissues were lower but had increased in some other tissues, such as heart (12.2 µg/g), brain (2.0 µg/g), gonads (25.8 µg/g), eyes (3.9 µg/g), spleen (5.5 µg/g), thyroid (6.2 µg/g), pituitary (21.3 µg/g) and subcutaneous fat (6.2 µg/g). At 24 hour, concentrations were less than 2 µg/g in all tissues except the intestinal tract (255.4 µg/g) and liver (10.5 µg/g). Concentrations in the tissues of the animal sacrificed at 48 hours were generally lower. Concentrations of radioactivity in most tissues were lower than those in plasma indicating that there was no specific accumulation or localisation of LAS and/or its metabolites in these tissues.

Plasma concentrations after subcutaneous doses: After single subcutaneous doses at a nominal dose level of 0.1 and 0.5 mg/kg bw mean plasma concentrations declined rapidly in the period 7.5--24 hours with a mean half-life of about 8 and 8.5 hours, respectively. After the first of 7 consecutive daily oral doses of 1 mg/kg bw, plasma levels declined to 0.28 µg/mL with a mean elimination half-life of about 10 hours. After the seventh and final dose, mean plasma concentrations declined until 24 hours with a mean half-life of about 13 hours.

Tissue distribution after repeated subcutaneous doses
Concentrations were generally highest at 2 hours when they were greatest in the intestinal tract (2.41 µg/g), kidneys (1.83 µg/g), lungs (2.45 µg/g), spleen (2.43 µg/g), thyroid (1.24 µg/g) and pituitary (1 µg/g). Concentrations in most tissues were generally lower at 4 hours except in the liver (1.74 µg/g) and kidneys (1.92 µg/g), organs associated with biotransformation and excretion. The relatively high concentrations of radioactivity in the gastrointestinal tract probably indicates the presence of material eliminated in the bile. At 24 hours, concentrations had declined in most tissues, but were highest in the liver (0.39 µg/g), kidneys (0.29 µg/g), lungs (0.27 µg/g) and adrenals (0.41 µg/g), although lower than those in plasma (0.49 µg/g). In the animal sacrificed at 48 hours, the plasma concentration (0.47 µg/g) was similar to that in the animal sacrificed at 24 hours and correspondingly the tissue concentrations were also similar, being highest in the liver (0.41 µg/g), kidneys (0.22 µg/g), lungs (0.23 µg/g) and adrenals (0.53 µg/g). Apart from the gastrointestinal tract, tissue concentrations of radioactivity were similar to or lower than the corresponding plasma concentrations at all times indicating that there was no specific accumulation or localisation of LAS and/or its metabolites in these tissues.

Details on excretion:

Excretion of oral doses: After single 30 mg/kg bw oral doses the radioactivity was rapidly excreted, mostly during the first 24 hours. Means of 71.2% and 23.1% of the dose were excreted in the urine and feces, respectively, during 5 days. Similarly, after single 1 mg/kg bw subcutaneous doses, means of 64.1% and 10.9% were excreted in urine and feces, respectively, during 5 days, mostly during the first 24 hours.About 5% of the dose was measured in the cage washings and cage debris and the mean overall recovery of radioactivity was 100.3%.


Excretion of subcutaneous doses: After single subcutaneous doses to rhesus monkeys at a dose level of 1.0 mg/kg bw, most of the dose was excreted within the first 48 hours. During the 5-day period after administration, means of 63.8% (males) and 64.3% (females) of the dose were excreted in the urine, (55.1% and 50.3% respectively in the first 24 hours) and means of 12.5% (males) and 9.2% (females) of the dose was excreted in the feces (4.9% and 1.6% respectively in the first 24 h). The mean total recovery of radioactivity in excreta and cage washings was 94.6%.

No unchanged LAS was detected in urine samples after oral or subcutaneous doses (either single or repeated).

Metabolites identified:

no

Details on metabolites:

Five metabolites were excreted for both oral and subcutaneous doses but they were not identified. Incubations with beta glucuronidase/sulfatase did not affect the metabolites, indicating that the metabolites were probably not present as the corresponding conjugates

Table 1: Mean rates of excretion of radioactivity in urine and faeces of rhesus monkeys after single oral dose of [14C] LAS at a nominal dose level of 30 mg/kg bw (Cresswell et al., 1978)

Results are expressed as percent dose

Time interval (hours)	Males^a		Females^a
	Urine	Faeces	Urine	Faeces
0-8	53.3	14.9	42.8	12.7
24-Aug	13.2		29.3
24-48	1.3	9.1	1.5	6.5
48-72	0.3	1.3	0.2	0.9
72-96	0.1	0.5	0.1	0.1
96-120	0.1	0.1	0.1	0.1
Total 0-120	68.3	25.9	74	20.3
Total recovery^b	100.1		100.5

a: Mean of 2 animals

b Includes radioactivity in cage washes and cage debris.

 

Table 2: Mean rates of excretion of radioactivity in urine and faeces of rhesus monkeys after single subcutaneous doses of [14C] LAS at a nominal dose level of 1 mg/kg bw(Cresswell et al., 1978)

Results axe expressed as percent dose

Time interval (hours)	Males^a		Females^a
	Urine	Faeces	Urine	Faeces
0-8	21.5	15.1	15.1
24-Aug	33.6	4.9	35.2	1.6
24-48	5.9	4.8	10.4	4.3
48-72	2.2	2	2.9	0.7
72-96	0.4	0.5	0.5	1.9
96-120	0.2	0.3	0.2	0.7
Total 0-120	63.8	12.5	64.3	9.2
Total recovery^b	95.6		93.5

a: Mean of 2 animals

b Includes radioactivity in cage washes and cage debris.

 

Table3: Concentrations of radioactivity in organs and tissues after 7 consecutive daily oral doses of [14C] LAS at a nominal dose level of 30 mg/kg bw(Cresswell et al., 1978)

Results are expressed asµg equivalents/g.

Organ or tissue	2 hour	4 hour	24 hour	48 hour
Stomach	238.6	93.1	1.9	0.2
Intestinal tract	108	156	255.4	10.8
Liver	64.8	52	10.5	15
Kidneys	135.6	81.2	1.9	0.6
Heart	7.5	12.2	0.8	0.6
Brain	0.7	2	0.3	0.8
Omentum/mesentery	10.2	12.1	1.9	0.9
Lungs	19.8	13.9	1.7	0.8
Gonads	7.6	25.8	0.9	0.7
Eyes	1.9	3.9	1	0.8
Spleen	4.6	5.5	1.1	0.4
Pancreas	17.7	16.8	0.4	0.4
Thyroid	4.1	6.2	< 0.3	< 0.3
Adrenals	20.6	11.5	1.3	1.5
Pituitary	17	21.3	< 0.3	<0.3
Spinal cord	1.2	0.9	< 0.3	0.3
Subcutaneous fat	2.3	6.2	< 0.3	0.5
Abdominal fat	NS	5.2	0.4	1.3
Muscle	2.4	1	< 0.3	< 0.3
Plasma	45.7	45.7	2.4	1

NS: no sample

 

Table 4: Concentrations of radioactivity in organs and tissues after 7 consecutive daily subcutaneous doses of [14C] LAS at a nominal dose level of 1.0 mg/kg bw(Cresswell et al., 1978)

Results are expressed as µg equivalents/g.  

Organ or tissue	2 hour	4 hour	24 hour	48 hour
Stomach	0.47	0.22	0.09	0.15
Intestinal tract	2.41	3.5	0.75	4.07
Liver	0.28	1.74	0.39	0.41
Kidneys	1.83	1.92	0.29	0.22
Heart	0.91	0.4	0.08	0.13
Brain	0.11	0.02	0.03	0.01
Omentum/mesentery	0.67	0.11	0.12	0.14
Lungs	2.45	0.75	0.27	0.23
Gonads	0.82	0.35	0.08	0.17
Eyes	NS	0.09	0.05	0.03
Spleen	2.43	0.4	0.2	0.19
Pancreas	0.76	0.34	0.16	0.06
Thyroid	1.24	0.29	0.1	0.04
Adrenals	0.82	0.85	0.41	0.53
Pituitary	1	0.27	0.17	0.17
Spinal cord	0.1	0.07	0.02	0.03
Subcutaneous fat	0.52	0.1	0.1	0.16
Abdominal fat	0.45	0.08	0.08	0.12
Muscle	0.12	0.1	0.02	0.02
Skin (site of injection)	113.96	19.26	2.42	6.67
Plasma	1.18	2.17	0.49	0.47

NS: no sample

Conclusions:

The disposition of radioactivity was studied in single and repeated oral or subcutaneous doses of [14C] LAS to rhesus monkeys. Results show that LAS is rapidly absorbed, then rapidly metabolized and excreted, primarily in the urine but also in the bile and feces. No accumulation or localization of radioactivity or change in elimination was observed. LAS does not bioaccumulate in the tissues.

Executive summary:

The purpose of the study was to determine the disposition of radioactivity after single and repeated oral or subcutaneous doses of [14C] LAS to rhesus monkeys.

 

Four adult rhesus monkeys (2 male and 2 female) of body weight approximately 5 kg each were used for all experiments. For excretion studies, single oral doses (14C-LAS of 30 mg/kg bw at 25 µCi) were administered by oral intubation as a solution in water. For the plasma level studies, the same animals were administered single oral doses (14C-LAS of 150 mg/kg bw at 26 µCi and 300 mg/kg bw at 28 µCi) at intervals of 2 -3 weeks. About 2 -3 weeks after the last saingle dose each animal received 7 consecutive daily oral doses of 14C-LAS (30 mg/kg bw/day at 28 µCi/day) in water (6 mL). Blood samples were taken, and animals were sacrificed at a different time after the last dose.

 

For subcutaneous dosing, single doses (14C-LAS of 1 mg/kg bw at 16-40 µCi), as a solution in water, were administered by injection into the subcutaneous tissue between the shoulder blades. Similarly, for the plasma level tests, the same animals received subcutaneous doses of 0.5 and 0.1 mg/kg bw (8 -22 and 2-5 µCi, respectively) at intervals of 2 -3 weeks. About 2 -3 weeks after the last single dose the animals received 7 consecutive daily subcutaneous doses of 1 mg/kg bw/day (about 24 µCi/day) in water. Blood samples were taken in both cases.

 

After single oral doses of 30, 150 and 300 mg/kg bw, peak plasma concentrations (at 4 hours in all cases) were very similar, with levels of 34, 41 and 36 µg/mL, respectively. Concentrations declined during the period of 6-24 hours, with a biological half-life of about 5-6 hours. After single subcutaneous doses of 0.1, 0.5 and 1 mg/kg bw, peak plasma concentrations increased almost proportionately, with levels of 0.16, 0.72 and 1.13 µg/mL, respectively. During seven consecutive daily oral (30 mg/kg bw/day) or subcutaneous (1 mg/kg bw/day) doses, there was no accumulation of radioactivity in plasma. Mean peak concentrations and biological half-lives were similar after the first and seventh doses. Two hours after the last dose, the highest radioactivity was observed in the stomach. Radioactivity was also observed in the intestinal tract, kidneys, liver, lung, pancreas, adrenals and pituitary. At 24 hours, concentrations were highest in the intestinal tract, probably indicating biliary excretion. Since the concentrations in the tissues in general were lower than in plasma, no specific accumulation of LAS occurred.

 

No unchanged LAS was detected in urine samples after oral or subcutaneous doses (either single or repeated). Five metabolites were excreted but they were not identified. Incubations with beta glucuronidase/sulfatase did not affect the metabolites, indicating that the metabolites were probably not present as the corresponding conjugates.

 

Based on the above, in single and repeated oral or subcutaneous disposition study of [14C] LAS with rhesus monkeys, LAS is rapidly absorbed, then rapidly metabolized and excreted, primarily in the urine but also in the bile and feces. No accumulation or localization of radioactivity or change in elimination was observed. LAS does not bioaccumulate in the tissues.

Reference 3

Endpoint:

dermal absorption in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study in peer-reviewed publication.

Justification for type of information:

A justification of the read-across approach is appended in Section 13.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Radiolabelled test substance (3 mM solution) was applied to the shaved skin of female rats. The exposure lasted 15 min, after which it was rinsed off. After a 24 hr observation period during feces, urine, and expired air was collected, the animals were sacrificed and the excised skin was examined by autoradiography.

GLP compliance:

not specified

Radiolabelling:

yes

Species:

rat

Strain:

other: Colworth-Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 100-120 g
- Housing: sealed metabolism cages
- Individual metabolism cages: yes

ENVIRONMENTAL CONDITIONS
- Air changes (per hr): 1.5 L/min

Type of coverage:

open

Vehicle:

other: Two test solutions were made: water, and 25% polyethylene glycol 400 in water.

Duration of exposure:

15 min

Doses:

- Nominal doses: 3 mM solution
- Dose volume: 0.2 ml

No. of animals per group:

no data

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: The test substance was added to the vehicle and homogenized and equilibrated at 40 degrees C for 24 hrs. The pH was then adjusted to 9.5 by adding 0.01 n NaOH or HCl.

TEST SITE
- Preparation of test site: 24 hrs before application, hair was removed with clippers. Only animals with intact skin were used.
- Area of exposure: 7.5 cm^2

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: yes: Animals were anesthetized during exposure. During the 24 hr observation period the animals were fitted with rest raining collars or non-occlusive patches. Non-occlusive patches were made of three layers of surgical gauze 1 cm larger in each dimension than the exposure area. Over this, a stainless steel 100 mesh gauze was placed and secured with surgical strapping with holes punctured in it.

SAMPLE COLLECTION
- Collection of urine and faeces: for 24 hrs after exposure
- Collection of expired air: for 24 hrs after exposure

SAMPLE PREPARATION
- Preparation details: feces were freezed dried, carcasses were homogenized in a blender and then freeze dried

ANALYSIS
- Method type(s) for identification: Liquid scintillation counting, excised skin was examined by autoradiography

Signs and symptoms of toxicity:

not specified

Dermal irritation:

not specified

Absorption in different matrices:

- Non-occlusive cover: < 2 micrograms
- Skin wash: 135 +/- 27 micrograms
- Skin test site: Heavy deposition was seen on the skin surface, and in the upper hair follicles, 11+/-4
micrograms
- Urine: none
- Faeces: none

Key result

Dose:

250 micrograms

Parameter:

percentage

Absorption:

< 0.3 %

Remarks on result:

other: 24 hrs after exposure

The amount of test substance that penetrated the skin was below the detection limit of 0.1 micrograms/cm² or less than 0.3% of the initial dose.

Conclusions:

The in vivo penetration through rat skin after a 15 min exposure was < 0.3%.

Executive summary:

Radiolabelled test substance (3 mM solution) was applied to the shaved skin of female rats. The exposure lasted 15 min, after which is was rinsed off. After a 24 hr observation period during feces, urine, and expired air was collected, the animals were sacrificed and the excised skin was examined by autoradiography. Results show that the test substance, which is of low solubility, did not penetrate through the skin to any significant degree. The amount of test substance penetrating the skin was below the detection limit. The penetration through rat skin was < 0.3%.

Reference 4

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study in peer-reviewed publication.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Radiolabelled test substance was applied (0.1 ml of a 3 mM solution) to samples of human abdominal skin from four female cadavers. Exposure time was 48 hrs. At 0.5, 1, 2, 3, 4, 6, 7, 8, 24, and 48 hrs analysis was done by liquid scintillation counting.

GLP compliance:

not specified

Radiolabelling:

yes

Species:

other: human

Sex:

female

Duration of exposure:

48 hrs

Doses:

0.1 ml of 3 mM solution

No. of animals per group:

four skin samples

Details on study design:

- Method for preparation of dose suspensions: The test substance was added to the vehicle and homogenized and equilibrated at 40 degrees C for 24 hrs. The pH was then adjusted to 9.5 by adding 0.01 n NaOH or HCl.

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: human cadavers
- Ethical approval if human skin:
- Type of skin: abdominal
- Preparative technique: Epidermal samples were heated at 58 degrees C for 2 min. Samples were placed in 1 cm diameter penetration cells, and saline with 0.012% penicillin, 0.01% streptomycin was placed on both surfaces of the cells. The cells were equilibrated at 37 degrees C for 24 hrs.
- Membrane integrity check: Only cells with electrical resistance greater than 50,000 ohms were used.
- Storage conditions: -70 degree C

Signs and symptoms of toxicity:

not examined

Dermal irritation:

yes

Remarks:

(some swelling was seen after 48 hrs of contact)

Absorption in different matrices:

Only 30% of the test substance was removed by rinsing, with 70 % remaining associated with the skin.

Dose:

152.9 micrograms/cm2

Parameter:

percentage

Absorption:

< 0.07 %

Remarks on result:

other: 2 hrs

Dose:

152.9 micrograms/cm2

Parameter:

percentage

Absorption:

< 0.07 %

Remarks on result:

other: 6 hrs

Dose:

152.9 micrograms/cm2

Parameter:

percentage

Absorption:

< 0.07 %

Remarks on result:

other: 24 hrs

Key result

Dose:

152.9 micrograms/cm2

Parameter:

percentage

Absorption:

< 0.07 %

Remarks on result:

other: 48 hrs

Conclusions:

The in vitro penetration through human skin after a 48 hr exposure was < 0.07%.152.9 micrograms/cm2.

Executive summary:

Radiolabelled test substance was applied (0.1 ml of a 3 mM solution) to samples of human abdominal skin from four female cadavers. Exposure time was 48 hrs. Analysis by liquid scintillation counting was done at 0.5, 1, 2, 3, 4, 6, 7, 8, 24, and 48 hrs. Penetration through human skin was negligible, with <0.07% absorbed in 48 hrs.

Description of key information

A series of toxicokinetics studies in rats and monkeys using C10-13 LAS and C12 LAS sodium salts suggest that MEA-LAS would be rapidly absorbed and distributed following intravenous or oral exposure, then rapidly eliminated from the body, mostly via the urine and to a lesser extent in the bile and faeces. 

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

80

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

Basic toxicokinetics

Study 1 (C10-13 LAS):   

The absorption, distribution, metabolism and elimination of C10 -13 LAS, sodium salt (radiolabelled with 35S) were studied in male Charles River rats. LAS was administered as an aqueous solution. The urine and faeces were collected and removed daily for analysis. At the termination of the study, the animals were killed and selected organs and tissues were taken for radio assay. In addition, the route of absorption was determined by oral feeding of 40 mg of LAS to thoracic duct-cannulated rats. The lymph was collected from each animal in a single 42-h fraction. The enterohepatic circulation of the surfactant was quantified by oral feeding of 1.2 mg of LAS to bile duct-cannulated rats and to rats. Three or five males per dose were used for the excretion test and six males for the absorption and enterohepatic tests. The compound was readily absorbed from the gastrointestinal tract (80-90% of the dose), and rapidly excreted with its metabolites, primarily in the urine. Specifically, most of the absorbed 35S was eliminated within 72 h and 60-65% of the absorbed dose was eliminated in the urine, 35% of the absorbed 35S was excreted in the bile and was reabsorbed completely from the gastrointestinal tract. Very little was found in the lymph, so transport of LAS is probably by way of portal venous blood. The authors suggested that metabolism proceeded via omega oxidation with subsequent catabolism through a beta-oxidation mechanism to form the metabolites that were excreted in the urine. Retention of radioactivity was not observed in any organ, so LAS had very low bioaccumulation potential under the conditions of the study (Michael, 1968). 

Study 2 (C10-13 LAS):   

In a toxicokinetics study, disposition of radiolabelled [14C] C10-13 LAS, sodium salt was studied via single and repeated oral or subcutaneous doses in Rhesus monkeys. Four adult monkeys (2 male and 2 female) of body weight approximately 5 kg each were used for all experiments. For excretion studies, single oral doses of 30 mg/kg bw (at 28 µCi) were administered by oral intubation as aqueous solutions. For the plasma level studies the same animals were administered single oral doses (150 mg/kg bw at 26 µCi and 300 mg/kg bw at 28 µCi) at intervals of 2 -3 weeks. About 2 -3 weeks after the last single dose each animal received 7 consecutive daily oral doses of the test substance (30 mg/kg bw/day at 28 µCi/day) in water. Blood samples were taken and animals were sacrificed at a different time after the last dose. Results show that the substance was rapidly absorbed, then rapidly metabolized and excreted, primarily in the urine but also in the bile and faeces. No accumulation or localization of radioactivity or change in elimination was observed, therefore, the test substance was not found to bioaccumulate in the tissues (Creswell, 1978).

Dermal absorption 

Study 1 (C12 LAS):    

The dermal absorption of [14C] radiolabelled C12 LAS, sodium salt was studied in rats and in isolated human epidermis. In the first part of the study, female Colworth-Wistar rats (n = 6) received a single dose (0.2 ml) of an aqueous suspension of the test substance (250 μg) applied to a 7.5 cm2 clipped area of the back. The contact time was 15 minutes, after which the test substance was rinsed off. The 14C levels in the skin and protective patch were determined 24 h after application and the penetration results based on levels of 14C excreted in urine, faeces and expired CO2 during the 24 h after application plus levels of 14C in the carcass of the animals at 24 h. No LAS was detected in skin (< 0.1 μg/cm2), indicating that less than 0.04% of applied dose was disposed in the skin (Howes, 1975).   

Study 2 (C12 LAS):    

In the second part of the above study (Howes, 1975), isolated human epidermis (0.78 cm2, n = 4) was exposed to 0.1 ml of a 1.2 mg/ml solution of the test substance C12 LAS, sodium salt. Penetration of 14C was measured at 2, 6, 24 and 48 h. No LAS was detected (<0.1 μg/cm2), indicating that less than 0.065% of the applied dose penetrated the skin in 48 h.