Sodium p-cumenesulphonate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June to July 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

adopted May 1983

Deviations:

no

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Sodium p-cumenesulphonate

EC Number:

239-854-6

EC Name:

Sodium p-cumenesulphonate

Cas Number:

15763-76-5

Molecular formula:

C9H12O3S.Na

IUPAC Name:

sodium 4-isopropylbenzenesulfonate

Test animals

Species:

mouse

Strain:

other: BOR:NMRI (SPF)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann, Borchen, Germany
- Age at study initiation: young adults
- Weight at study initiation: 30.4 +/- 1.7 g (males); 24.3 +/- 1.5 g (females)
- Fasting period before study: no
- Housing: 5 animals per cage, gender separated, macrolone cages Type III
- Diet : Ssniff R10 exclusive diet for rats (ad libitum); supplied by Ssniff Spezialfutter GmbH, Soest, Germany
- Water: drinking water (ad libitum)
- Acclimation period: one week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 +/- 3
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12IN

-LIFE DATES: From: July 9, 1991 To: July 18, 1991

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

Water

Details on exposure:

Concentration of test material in vehicle: 40 %

Frequency of treatment:

Single oral application
The application took place once orally using a tuberculin syringe and stomach tube.
The application volume was 16 cm3 / kg body weight for the test substance and the Negative control and 10 cm3 / kg body weight for the positive control.

Post exposure period:

24, 48 and 72 hours

Doses / concentrations

Dose / conc.:

4 467 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide
Route of administration: oral by gavage
- Dose: 100 mg/kg bw
- Vehicle: water
- Total application volume: 10 ml/kg bw
- post exposure period: 24 hours

Examinations

Tissues and cell types examined:

bone marrow; polychromatic erythrocytes (PCE), normochromatic erythrocytes (NCE)

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: The maximum tolerable dose (MTD)* was selected as dose.The MTD was determined in a dose range finding study. *MTD is defined as dose with no mortality but clear clinical symptoms within 3 days after application
Phase 1: Limit test with 5000 mg/kg bw
Phase 2: Determination of the MTD range with reduced animal number
Phase 3: Determination of the MTD with 5 animals/sex/dose

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields): 24, 48 and 72 hours after treatment the animals were killed by cervical dislocation and tissue was sampled.

DETAILS OF SLIDE PREPARATION
The femora were removed and the bone marrow was suspended in fetal calf serum. The cell suspensions were centrifuged with 160 x g for 5 minutes and the supernatand discarded. The serum was resuspended and the suspension purified using a cellulose chromatographic column. The eluate was centrifuged at 800 x g for 10 minutes and the pellet in fetal calf serum /25 mM EDTA suspended. From this suspension 3-4 smears per animals were prepared on slides which were dried for at least 24 hours and stained with May-Grünwald/Giemsa solution.

METHOD OF ANALYSIS
The cell analysis was performed by means of a Zeiss miscroscope at a 1000fold magnification (oil immersion). At least 1000 polychromatic erythrocytes (PCE) per animal were examined to determine the frequency of micronucleated cells. The ratio of PCE to normochromatic cells (NCO) was determined for a sample of 1000 erythrocytes. The number of micronucleated cells in counted NCE was determined.

Evaluation criteria:

For the identification of micronuclei the following criteria were considered:a) roundish and clear contour by the nuclear membraneb) diameter of about 1/20 of the size of the polychromatic erythrocytec) lays in the same focus layer as the observed erythrocyteThe micronucleus test is regarded as positive (test substance induces micronuclei in polychromatic erythrocytes) if the frequency of mucronucleated polychromatic erythrocytes of at least one tretament group is statistically significantly increased compared to the negative control and the increase is biologically relevant.

Statistics:

Mean values and standard deviations were calculated for the following parameters: a) number of polychromatic erythrocytes (PCE) containing micronucleib) ratio of PCE/NCEComparison of treatment groups with different post exposure periods with negative controls of respective post exposure periods. After control of the relative frequency of micronuclei in the treatment groups on homogeneity with the mean relative frequency a statistical analysis of micronucleus frequency using a 2 x 2 contingency table with chi² test and continuity table according to Yates was performed (see [1]).The differences of miconucleus frequencies in the positive control were reassessed in the two-sided t-test. This test was also used for the statistical analysis of the PCE/NCE-ratio.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE- FINDING STUDY
- Dose range:
Phase 1: males and females: 5000 mg/kg bw (limit test);
Phase 2: males: 1585, 1995, 2512, 3162 and 3981 mg/kg bw; females: 3162, 3548, 3981, 4467 and 5000 mg/kg bw.
Phase 3: males and females: 3981, 4467 and 5000 mg/kg bw.

- Clinical signs of toxicity in test animals:
Phase 1: 4/5 male and 1/5 female animals died. The males died within 4 hours after application, the female died within 24 hours after application of the test substance. Clinical signs as hunched posture, ruffled fur, closed eyes and diarrhea were observed.
Phase 2: 1/5 female at 3981 mg/kg bw died. At high doses clinicals signs as hunched posture, ruffled fur, closed eyes and diarrhea were observed.
Phase 3: 2/5 male and 2/5 female animals died at 5000 mg/kg bw. At 4467 mg/kg bw no mortality occured but severe toxic effects were found.

RESULTS OF DEFINITIVE STUDY
- Clinical signs of toxicity in test animals: Hunched posture, ruffled fur, closed eyes and diarrhea were observed. One day after application the effects subsided and two days after application all animals were free of clinical symptoms. One male and one female animal died 24 and 5.5 hours after application, respectively. These animals were replaced with mice of a concurrent satellite group also treated with the test substance. One male of the satellite group died 5 hours after application.

- Induction of micronuclei:
Positive control: Significantly increased number of polychromatic erythrocytes (PCE) with miconuclei both in male and female animals.
Test substance: No significant increase in the number of PCE with micronuclei after 24 and 48 hours in both males and females and after 72 hours in males. After 72 hours a statistically significant increase of the number of micronuclei in PCEs in females were observed. If the results of males and females were combined no significant difference in the frequency of micronuclei between treatment group and combined vehicle control group is observed. (Tables 1, 2 and 3).

- Ratio of PCE/NCE: Neither in the positive control group nor in the treated males a significant difference of PCE/NCE ratio compared to the control group is observed. In the females of the treatment groups no difference was observed 24 and 48 hours after treatment. After 72 hours the PCE/NCE ratio was decreased compared to vehicle control group but still was above the typically observed ratio of 1.0. (Tables 1, 2 and 3)

- Appropriateness of dose levels and route: The selected dose level investigated as the maximum tolerable dose (MTD) induced clear toxic symptoms and was lethal in two animals. According to the guideline the recommended criteria for the dose level were fulfilled. The route of administration was appropriate as systemic availability could be demonstrated by clinical signs.

All male mice treated with the test substance showed no statistically significant increase in micronucleus frequency at any sampling time compared to control animals. For the female mice treated with the test substance at sampling times 24 and 48 hours after treatment also no statistically significant increase in micronucleus frequency was observed. Only at sampling time point 72 hours a statistically significant increase of polychromatic erythrocytes with micronuclei compared to control animals was observed. This effect was regarded as biologically not relevant as this increase ís based on the exceptional low micronucleus frequency of vehicle control group. Sodium cumenesulphonate under these test conditions is regarded as not mutagenic in the micronucleus test.

Any other information on results incl. tables

The statistically significant increase in frequency of micronuclei is considered to be of no biological relevance for the following reasons:

- The frequency of micronuclei at this sampling time point (0.18%) is not above the frequency of micronuclei of controls generally observed in this test laboratory (0.07 - 0.22%). The statistical significance in this case is caused by the low frequency of micronuclei in the control group (0.02%) which deviates downwards from the so far observed frequencies for controls. After addition of male and female animals of sampling time point 72 h into one group there is no more a statistically significant difference.

- A delayed effect based on slow excretion is improbable for sodium cumenesulphonate as sulphonic acids in general are readily absorbed and do not show any tendency for accumulation. But this kind of detention is regarded as prerequisite to explain based on the kinetic of erythrocyte maturation an impact on micronuclei frequency at sampling time point of 72 hours.

 

The results of the positive control affirm the sensitivity of the mouse strain to mutagenic substances. The frequency of micronuclei in polychromatic erythrocytes was considerably increased compared to the control group.

 

Table 1: Results of in vivo micronucleus test for male animals (mean ± standard deviation)

 

		Neg. control			test substance 4467 mg/kg bw			Pos. control
sampling time		24 h	48 h	72 h	24 h	48 h	72 h	24 h
micronuclei in 1000 PCE		0.8  ± 0.8	1.8  ± 0.8	0.4 ± 0.5	0.6 ± 0.5	0.8  ± 0,8	0.2  ± 0.4	48.0* ± 19.6
% PCE with micronuclei		0.08	0.18	0.04	0.06	0.08	0.02	4.8
PCE / NCE		1.0 ± 0.2	1.4 ± 0.3	1.6 ± 0.3	1.0 ± 0.3	1.1 ± 0.4	1.9 ± 0.9	0.8  ± 0.1

*p < 0.05

 

Table 2: Results of in vivo micronucleus test for female animal (mean ± standard deviation)

 

		Neg. control			test substance 4467 mg/kg bw			Pos. control
sampling time		24 h	48 h	72 h	24 h	48 h	72 h	24 h
micronuclei in 1000 PCE		1.4  ± 1.7	1.8  ± 1.1	0.2 ± 0.4	2.2 ± 1.1	1.2  ± 0,8	1.8*  ± 1.5	36.8* ± 9.8
% PCE with micronuclei		0.14	0.18	0.02	0.22	0.12	0.18	3.6
PCE / NCE		1.2 ± 0.2	1.4 ± 0.2	2.4 ± 0.6	1.0 ± 0.2	1.3 ± 0.3	1.3 ± 0.5	1.0  ± 0.1

*p< 0.05

 

Table 3: Results of in vivo micronucleus test for male + female animals (mean ± standard deviation)

 

		Neg. control			test substance 4467 mg/kg bw			Pos. control
sampling time		24 h	48 h	72 h	24 h	48 h	72 h	24 h
micronuclei in 1000 PCE		1.1  ± 1.3	1.8  ± 0.9	0.3 ± 0.5	1.4 ± 1.2	1.0  ± 0.8	1.0  ± 1.3	42.4* ± 15.7
% PCE with micronuclei		0.11	0.18	0.03	0.14	0.10	0.10	4.24
PCE / NCE		1.1 ± 0.2	1.4 ± 0.3	2.0 ± 0.6	1.0 ± 0.2	1.2 ± 0.4	1.6 ± 0.8	0.9  ± 0.1

* p < 0.05

Applicant's summary and conclusion

Conclusions:

Negative

Executive summary:

The potential of Sodium p-cumenesulphonate to cause cytogenetic damage which results in the formation of micronuclei containing lagging chromosome fragments or whole chromosomes was assessed following official guideline OECD 474, Mammalian Erythrocyte Micronucleus Test. The statistically significant increase in frequency of micronuclei is considered to be of no biological relevance.