Potassium nitrite

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

Data is from publication

Data source

Reference

Reference Type:

publication

Title:

EVALUATION OF THE ORAL TOXICITY OF POTASSIUM NITRITE IN A 13-WEEK DRINKING-WATER STUDY IN RATS

Author:

H. P. TIL, H. E. FALKE, C. F. KUPER and M. I. WILLEMS

Year:

1988

Bibliographic source:

Food and chemical toxicology

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: As mentioned below

Principles of method if other than guideline:

To determine Subchronic oral toxicity study of test chemical on Rats.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Potassium nitrite

EC Number:

231-832-4

EC Name:

Potassium nitrite

Cas Number:

7758-09-0

Molecular formula:

HNO2.K

IUPAC Name:

potassium nitrite

Test material form:

solid

Details on test material:

- Name of test material (IUPAC name): Potassium nitrite
- Molecular formula: KNO2
- Molecular weight: 85.103 g/mol
- Smiles notation: N(=O)[O-].[K+]
- InChl: 1S/K.HNO2/c;2-1-3/h;(H,2,3)/q+1;/p-1
- Substance type: Organic
- Physical state: Solid

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Weanling, Wistar derived SPF-bred rats (Bor; WlSW)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann (Institute for the Breeding of Laboratory Animals GmbH & Co. KG, Borchen, FRG).
- Females (if applicable) nulliparous and non-pregnant:yes
- Age at study initiation: 6 weeks old
- Weight at study initiation: NA
- Fasting period before study: NA
- Housing: The rats were housed under conventional conditions, in suspended stainless-steel cages fitted with a wire-mesh floor and front.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 13 days

DETAILS OF FOOD AND WATER QUALITY: All rats were fed the Institute's grain-based open-formula diet (with a nitrite and nitrate content of 2 and 140mg/kg, respectively)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 + 2°C
- Humidity (%): 40-70%
- Air changes (per hr): 10/hr
- Photoperiod (hrs dark / hrs light): 12hr light/dark cycles

IN-LIFE DATES: From: To:

Administration / exposure

Route of administration:

oral: drinking water

Details on route of administration:

The rats received potassium nitrite in the drinking-water (tap-water; nitrite and nitrate content <0.01 and 10mg/litre, respectively) at levels of 0 (negative control), 100, 300, 1000 and 3000mg/litre.

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Rate of preparation of diet (frequency): Test solutions and tap-water were freshly supplied to the rats in glass bottles every day.
- Mixing appropriate amounts with (Type of food): Drinking water
- Storage temperature of food: NA

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: nitrite and nitrate content <0.01 and 10mg/litre
- Amount of vehicle (if gavage): NA
- Lot/batch no. (if required): NA
- Purity:NA

Additional information: The potassium concentrations in the nitrite solutions were equalized by adding KCl up to the K+ level of the 3000 mg KNO2/litre solution.
An additional group received drinking-water supplemented with KCl only, to achieve the same K+ concentration as that found in the 3000 mg KNO2/litre solution.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 weeks (91 days)

Frequency of treatment:

Everyday

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/L drinking water

Remarks:

Negative control

Doses / concentrations 2

Dose / conc.:

100 mg/L drinking water

Doses / concentrations 3

Dose / conc.:

300 mg/L drinking water

Doses / concentrations 4

Dose / conc.:

1 000 mg/L drinking water

Doses / concentrations 5

Dose / conc.:

3 000 mg/L drinking water

No. of animals per sex per dose:

ten rats of each sex/group (Five treatment groups )

Control animals:

yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes / No / Not specified
- Time schedule:

BODY WEIGHT: Yes / No / Not specified
- Time schedule for examinations: The rats were weighed at weekly intervals and were observed daily for condition and behaviour

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes / No / Not specified
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / Not specified

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / Not specified

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes / No / Not specified
- Time schedule for examinations: Food and liquid intake were measured over weekly periods throughout the study

OPHTHALMOSCOPIC EXAMINATION: Yes / No / Not specified
- Time schedule for examinations: Ophthalmoscopic observations were made in all rats of the control and top-dose groups prior to the administration of the test substances and during wk 13.
- Dose groups that were examined:

URINALYSIS: Yes / No / Not specified
- Time schedule for collection of urine: In wk 9 of treatment urine was collected over a 24-hr period from all rats, except those receiving unsupplemented tap-water
- Metabolism cages used for collection of urine: Yes It was collected in calibrated tubes under cooling on dry ice. Its volume was determined and it was examined for
creatinine and nitrite and nitrate

Sacrifice and pathology:

Early in wk 14, the rats were killed by exsanguination from the abdominal aorta whilst under light ether anaesthesia, and a thorough autopsy was performed.

Statistics:

Data on body weight were evaluated by a oneway analysis of covariance, followed by Dunnett's multiple comparison tests

Results and discussion

Results of examinations

Clinical signs:

not specified

Mortality:

no mortality observed

Description (incidence):

There were no deaths and the rats appeared to be healthy throughout the study

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight was decreased at 3000 mg/l in males.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Growth and food intake were significantly decreased in the 3000-mg/litre group in males.

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

Food efficiency was decreased in the 3000-mg/litre group in males. (data not shown).

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

effects observed, treatment-related

Description (incidence and severity):

Liquid intake was clearly diminished in the 3000- and the 1000-mg/litre groups of males and in the 3000-mg/litre group of females

Ophthalmological findings:

no effects observed

Description (incidence and severity):

Ophthalmoscopic examination did not reveal any differences between the test rats and controls that could be ascribed to treatment

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Haemoglobin concentration, packed-cell volume and erythrocyte count were slightly decreased in the males receiving 1000 and 3000mg/litre, and in the females receiving 1000 mg/litre. In females, the erythrocyte count was also decreased with a dose of 3000 mg/litre which was accompanied by increases in mean corpuscular volume and mean corpuscular haemoglobin. Methaemoglobin concentration was significantly increased with 3000mg/litre in both sexes

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

With the 3000-mg/litre treatment the plasma urea level was increased in males, while the plasma alkaline phosphatase activity was slightly decreased in both sexes, although the difference was statistically significant in females only (Table 3). There was a decrease in plasma aspartate aminotransferase in the females given 1000 and 3000 mg/litre in comparison to the KCI group, but not as compared with the controls receiving unsupplemented drinking-water

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

The volume of the urine produced during 24 hr decreased with increasing nitrite levels in the drinking-water, the differences from the controls being statistically significant in males treated with 3000 mg/litre and in females treated with 300 mg/litre and above . The urine concentration test revealed an increase in the density of the urine of the animals treated with 3000mg/litre in both sexes, accompanied by a decrease in urine production in males . Excretion levels of creatinine and
nitrate did not show treatment-related differences among the groups and nitrite was not found in the urine of any of the groups. There was no evidence of
increased mutagenic activity in the urine of rats receiving 3000 mg/litre, either in the presence or in the absence of S-9 mix and fl-glucuronidase.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

The absolute and relative weights of the kidneys and spleen in females and the relative weight of the kidneys in males were increased in the group receiving 3000 mg/litre. The increase in the relative brain weight in males receiving 3000 mg/iitre is ascribed to the lower body weight in this group and the well-known inverse correlation between body weight and relative brain weight

Gross pathological findings:

not specified

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Histopathological examination of all other organs was essentially negative.

Histopathological findings: neoplastic:

not specified

Other effects:

not specified

Effect levels

1

Key result

Dose descriptor:

NOEL

Effect level:

< 100 mg/L drinking water

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

clinical biochemistry

food consumption and compound intake

food efficiency

haematology

ophthalmological examination

organ weights and organ / body weight ratios

urinalysis

water consumption and compound intake

2

Dose descriptor:

NOAEL

Effect level:

300 mg/L drinking water

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

mortality

3

Dose descriptor:

LOAEL

Effect level:

1 000 mg/L drinking water

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

mortality

Target system / organ toxicity

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

A subchronic oral toxicity study with test chemical was carried out in groups of ten male and ten female 6-wk-old rats. No mortality observed and the rats appeared to be healthy throughout the study. Effects were observed in food and water consumption, opthalological and haematological effects were observed. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.

Executive summary:

A subchronic oral toxicity study with test chemical was carried out in Wistar derieved SPF Bred rats. Groups of ten male and ten female 6-wk-old rats received test chemical in the drinking-water (tap-water) at levels of 0, 100, 300, 1000 and 3000mg/litre for a period of 13 week. The potassium concentration in the nitrite solutions was equalized by adding potassium chloride (KCL) up to the potassium level of the 3000 mg /litre solution. An additional group of ten males and ten females received drinking-water supplemented with KCI only, at an amount resulting in a potassium concentration equivalent to that of the 3000 mg /litre solution. No mortality observed and the rats appeared to be healthy throughout the study. Ophthalmoscopic examination did not reveal any differences between the test rats and controls that could be ascribed to treatment. Body weight, food intake and food efficiency were decreased at 3000-mg/litre level in males, while liquid intake was decreased in males given 1000 and 3000 mg/litre and in females given 3000 mg/litre. There was a significant increase in the methaemoglobin concentration in animals given 3000 mg/litre, while slight decreases in red blood cell variables occurred at the 1000 and 3000 mg/litre dose. No impaired renal function was observed in any of the test groups, although the relative weight of the kidneys and the plasma urea nitrogen level was increased at 3000 mg/litre. There was a slight decrease in plasma alkaline phosphatase activity at 3000 mg/litre. A small amount of nitrite was present in the saliva of the rats receiving 3000 mg/litre but there was no evidence of increased mutagenic activity in the urine of these rats. Interestingly, hypertrophy of the adrenal zone glomerulosa was observed in all test groups, the incidence and degree being dose related. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.