Sodium pyruvate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2015

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Version / remarks:

2009

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium pyruvate

EC Number:

204-024-4

EC Name:

Sodium pyruvate

Cas Number:

113-24-6

Molecular formula:

C3H4O3.Na

IUPAC Name:

sodium 2-oxopropanoate

Test material form:

solid

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories (Raleigh, NC)
- Females nulliparous and non-pregnant: yes
- Weight at study initiation: 248.5-250.2 g (males) and 199.5-200.2 g (females)
- Housing: housed in pairs in cages with softwood granulate bedding and environmental enrichment was provided
- Diet: gamma-irradiated pellet diet, ad libitum
- Water: sterilized drinking water, ad libitum
- Acclimation period: ≥ 17 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-22
- Humidity (%): 52-55
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: phosphate-buffered saline (PBS)

Mass median aerodynamic diameter (MMAD):

ca. 1.5 µm

Geometric standard deviation (GSD):

1.75

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: flow-past nose-only exposure chambers
- System of generating particulates/aerosols: Aerosols were generated by Collison Nebulizers and diluted with filtered conditioned fresh air.
- Air flow rate: continuous flow rate
- Method of particle size determination: Aerodynamic particle size (APS) spectrometer

TEST ATMOSPHERE
- Brief description of analytical method used: Levels of pyruvate were measured by enzymatic means by a commercial Pyruvate Detection kit (Cayman Chemicals, Ann Arbor, MI) in total particulate matter (TPM) samples of the aerosols collected on Cambridge filter pads.

VEHICLE
- Composition of vehicle: phosphate-buffered saline

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Levels of pyruvate were measured by enzymatic means by a commercial Pyruvate Detection kit (Cayman Chemicals, Ann Arbor, MI) in total particulate matter (TPM) samples of the aerosols collected on Cambridge filter pads. Sampled were taken at least 3 times a day with a sampling time of 20 minutes. The analytical method used was an indirect enzymatic fluorescence assay.

Duration of treatment / exposure:

6 hours / day

Frequency of treatment:

5 days / week

Doses / concentrations

Dose / conc.:

0.034 mg/L air

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

yes, sham-exposed

Details on study design:

- Dose selection rationale: a range finding study was performed

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations included check for mortality and health status

DETAILED CLINICAL OBSERVATIONS: Not specified

BODY WEIGHT: Yes
- Time schedule for examinations: at least twice a week

FOOD CONSUMPTION:
- Food consumption was determined by gravimetry once a week.

FOOD EFFICIENCY: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on day 28
- Anaesthetic used for blood collection: Yes, pentobarbital
- Animals fasted: No
- How many animals: all animals
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on day 28
- Animals fasted: No
- How many animals: all animals
- Parameters checked in table 2 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: once during the study
- Metabolism cages used for collection of urine: Not specified
- Animals fasted: No
- Parameters checked in table 3 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see table 4 and table 5)

Results and discussion

Results of examinations

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

no effects observed

Description (incidence and severity):

All rats had an increase in body weight throughout the exposure period. No effects compared with sham groups were observed.

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

No exposure-related effects were observed in male and female rats.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No exposure-related effects were observed in male and female rats.

Urinalysis findings:

not specified

Description (incidence and severity):

A fecal contamination occured. Therefore, data were not reported.

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Spleen weights in female rats elicited a different response, with higher weights after exposure to sodium pyruvate. This result in females, however, appeared to be due to the low spleen weight in the sham group. No exposure-related effects were observed in male and female rats.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were several macroscopic observations of organs at necropsy; but they were specifically related to neither treatment nor exposure concentration.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

In the mid-base of epiglottis a slight increase in ventral-squamous hyperplasia was observed in males exposed to sodium pyruvate. Overall cytoplasmic vacuolation of hepatocytes was observed in the livers of most rats of the study, and increased vacuolation could be observed in rats exposed to sodium pyruvate. Vacuolation was increased in the livers of female rats that inhaled sodium pyruvate compared with sham and PBS control females, but this difference was small. A similar effect was not seen in males, and sodium pyruvate was not considered to have contributed to this change.

Histopathological findings: neoplastic:

no effects observed

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

0.034 mg/L air

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: No adverse effects observed up to the highest concentration tested.

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

Table 6: Organ weights in male rats

		Sham	PBS	Sodium Pyruvate
Liver	g	11.77 ± 0.391	12.19 ± 0.455	12.08 ± 0.360
	X10E-4	348.97 ± 7.986	371.22 ± 7.420	362.39 ± 7.275
	N	10	10	10
Spleen	g	0.69 ± 0.040	0.73 ± 0.099	0.65 ± 0.031
	X10E-4	20.61 ± 1.173	22.40 ± 3.130	19.53 ± 0.942
	N	10	10	10
Left adrenal	g	0.03 ± 0.009	0.02 ± 0.002	0.03 ± 0.001
	X10E-4	0.97 ± 0.257	0.75 ± 0.078	0.78 ± 0.036
	N	10	8	10
Right adrenal	g	0.02 ± 0.002	0.03 ± 0.001	0.02 ± 0.001
	X10E-4	0.73 ± 0.045	0.77 ± 0.036	0.71 ± 0.030
	N	9	9	10
Left kidney	g	1.07 ± 0.032	1.04 ± 0.055	1.03 ± 0.021
	X10E-4	31.89 ± 0.722	31.95 ± 1.688	30.92 ± 0.713
	N	10	10	10
Right kidney	g	1.09 ± 0.031	1.08 ± 0.056	1.03 ± 0.026
	X10E-4	32.20 ± 0.738	33.10 ± 1.812	31.07 ± 0.629
	N	10	10	10
Thymus	g	0.31 ± 0.021	0.31 ± 0.023	0.34 ± 0.026
	X10E-4	9.12 ± 0.598	9.43 ± 0.583	10.23 ± 0.776
	N	10	10	10
Lung/Larynx/ Trachea	g	1.40 ± 0.025	1.44 ± 0.047	1.46 ± 0.047
	X10E-4	41.76 ± 1.064	44.21 ± 1.480	44.08 ± 1.950
	N	10	9	10
Brain	g	2.05 ± 0.023	2.04 ± 0.072	2.08 ± 0.033
	X10E-4	60.94 ± 1.146	62.21 ± 2.088	62.39 ± 0.955
	N	10	10	10
Heart	g	1.07 ± 0.034	1.08 ± 0.025	1.07 ± 0.020
	X10E-4	31.82 ± 0.760	33.08 ± 0.491	32.18 ± 0.802
	N	10	10	10
Left testis	g	1.63 ± 0.046	1.36 ± 0.140	1.66 ± 0.025
	X10E-4	48.25 ± 1.204	41.74 ± 4.378	50.00 ± 1.204
	N	10	10	10
Right testis	g	1.61 ± 0.051	1.38 ± 0.142	1.61 ± 0.034
	X10E-4	47.94 ± 1.358	42.12 ± 4.429	48.62 ± 1.433
	N	10	10	10

Absolute and relative body weight, mean ± SD

Table 7: Organ weights in female rats

		Sham	PBS	Sodium Pyruvate
Liver	g	9.17 ± 0.387	10.02 ± 0.507	9.50 ± 0.293
	X10E-4	388.30 ± 11.643	418.08 ± 21.681	406.83 ± 8.813
	N	10	10	10
Spleen	g	0.46 ± 0.027	0.61 ± 0.069+	0.55 ± 0.028*
	X10E-4	19.80 ± 1.060	25.50 ± 3.115	23.64 ± 1.095*
	N	9	9	10
Left adrenal	g	0.04 ± 0.013	0.04 ± 0.001	0.03 ± 0.001
	X10E-4	1.85 ± 0.486	1.53 ± 0.045	1.42 ± 0.048
	N	9	9	10
Right adrenal	g	0.03 ± 0.002	0.03 ± 0.001	0.03 ± 0.001
	X10E-4	1.27 ± 0.105	1.31 ± 0.056	1.42 ± 0.048
	N	8	9	10
Left kidney	g	0.77 ± 0.016	0.85 ± 0.059	0.78 ± 0.019
	X10E-4	33.01 ± 0.629	35.69 ± 2.555	33.37 ± 0.585
	N	9	9	10
Right kidney	g	0.78 ± 0.017	0.83 ± 0.037	0.82 ± 0.017
	X10E-4	33.35 ± 0.618	34.89 ± 1.603	35.02 ± 0.688
	N	9	9	10
Thymus	g	0.35 ± 0.034	0.45 ± 0.103	0.33 ± 0.024
	X10E-4	14.81 ± 1.412	18.24 ± 4.025	14.22 ± 0.900
	N	10	9	10
Lung/Larynx/ Trachea	g	1.27 ± 0.036	1.56 ± 0.175	1.19 ± 0.026
	X10E-4	53.86 ± 1.382	64.77 ± 6.851	51.10 ± 1.212
	N	9	9	10
Brain	g	1.85 ± 0.091	2.00 ± 0.034	1.89 ± 0.034
	X10E-4	79.00 ± 4.427	83.52 ± 1.590	81.25 ± 2.316
	N	10	8	10
Heart	g	0.91 ± 0.073	0.83 ± 0.062	0.82 ± 0.021
	X10E-4	38.46 ± 2.629	34.59 ± 2.830	35.40 ± 0.876
	N	10	10	10

 Absolute and relative body weight, mean ± SD, *p<0.05

Applicant's summary and conclusion

Conclusions:

No treatment-related effects were observed in Sprague-Dawley rats after inhalative nose-only exposure to sodium pyruvate (33.9 µg/L) for 28 days, 6 h/day, 5 days/week.

Executive summary:

A sub-chronic inhalation study according to OECD guideline 412 was performed with Sprague-Dawley rats. The rats were nose-only exposed, 6 h/day, 5 days/week for 28 days to filtered air, saline, nicotine (50 µg/L), sodium pyruvate (33.9 µg/L) or equimolar nicotine/pyruvic acid mixtures (18, 25 and 50 µg nicotine/L).

After exposure to sodium pyruvate no exposure-related effects on body weight, haematological parameters and clinical parameters were observed. Spleen weights in female rats elicited a different response, with higher weights after exposure to sodium pyruvate. This result in females, however, appeared to be due to the low spleen weight in the sham group. No further changes in organ weights were observed after exposure to sodium pyruvate. No treatment-related gross pathological findings were revealed after inhalation of sodium pyruvate. In the mid-base of epiglottis a slight increase in ventral-squamous hyperplasia was observed in males exposed to sodium pyruvate. Overall cytoplasmic vacuolation of hepatocytes was observed in the livers of most rats of the study, and increased vacuolation could be observed in rats exposed to sodium pyruvate. Vacuolation was increased in the livers of female rats that inhaled sodium pyruvate compared with sham and PBS control females, but this difference was small. A similar effect was not seen in males, and sodium pyruvate was not considered to have contributed to this change. These results suggest that aerosols of sodium pyruvate did not result in substantial toxicity.