Zinc selenite

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

publication

Title:

Nodular regenerative hyperplasia in the rat induced by a selenium-enriched diet: Study of a model.

Author:

Bioulac-Sage P.; et al.

Year:

1992

Bibliographic source:

Hepatology 16, 418-425

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Weaned male rats were fed diets containing 0.4 (control), 2 or 4 ppm selenium for 2 months.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium selenite

EC Number:

233-267-9

EC Name:

Sodium selenite

Cas Number:

10102-18-8

Molecular formula:

H2O3Se.2Na

IUPAC Name:

disodium selenite

Details on test material:

- Name of test material (as cited in study report): Na2SeO3
- Molecular formula (if other than submission substance): Na2SeO3
- Molecular weight (if other than submission substance): 172.96 g/mol
- Physical state: solid
- no further information given

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Orleans, France
- Age at study initiation: not stated
- Weight at study initiation: 50 g
- Housing: in plastic cages (5/cage)
- Diet: free access to food
- Water: free access to water
- Acclimation period: not stated

ENVIRONMENTAL CONDITIONS
- Temperature (°C):
- Humidity (%):
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light):

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: diet

Details on oral exposure:

DIET PREPARATION
The composition of the diet (INRA, Jouy-en-Josas, France) was the following: cornstarch, 44.26%; purified casein, 22%; saccharose, 22.13%; cellulose, 2%; peanut oil, 2.5%; colza oil, 2.5%; minerals, 3.5%; vitamins, 1%; D-L methionine, 0.13%; and Selenium (sodium selenite, Na2S2O3) (group 1: 0.4 ppm, group 2: 2 ppm, group 3: 4 ppm).

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

2 months

Frequency of treatment:

continuously (in diet)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.4 ppm Se (group 1, control diet)
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
2 ppm Se (group 2)
Basis:
nominal in diet

Doses / concentrations 3

Remarks:

Doses / Concentrations:
4 ppm Se (group 3)
Basis:
nominal in diet

No. of animals per sex per dose:

group 1: n=5; group 2: n=8; group 3: n=8

Control animals:

yes

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: weekly.

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: No data.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data.

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: No data.

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: Yes
- Anaesthetic used for blood collection: under pentobarbital anaesthesia.
- Animals fasted: No data.
- Parameters checked: total bilirubin, AST, ALT, alkaline phosphatase and y-glutamyltransferase portal

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER: Yes
- Portal pressure was measured on a manometer with a 3F infusion catheter inserted through the mesocolic vein into the portal vein.

Sacrifice and pathology:

All rats were killed two months after the start of the experiment.

GROSS PATHOLOGY : Yes
- Livers were immediately removed and weighed. Part was fixed in 10% neutral formalin and routinely processed for light microscopy.
- Spleens were then removed and weighed.

HISTOPATHOLOGY: Yes
- Slides were stained with haematoxylin-eosinsaffron (HES), reticulin and picro Sirius red. Part of a lobe was perfusion-fixed through a hepatic vein (10 cm H,O) with 1.5% glutaraldehyde and then routinely processed for electron microscopy. One-micrometer sections were stained with toluidine blue. Selected areas from nodular (nodules and atrophic hepatocytes) and nonnodular zones were used for ultrathin sections. Grids were double-contrasted with uranyl acetate and lead citrate and examined under a Philips CMlO electron microscope (Centre de Microscopie Electronique, Universite de Bordeaux II).
- When it became apparent that in group 3 some liver lobes were atrophic whereas others were hypertrophic, lobes were weighed and fixed separately for light microscopy only.

Other examinations:

MORPHOMETRICAL STUDIES
A camera lucida was used, magnification x125, connected to an IBAS semiautomatic image analysis system (Karl Zeiss, Oberkochen, Germany) to examine individual HES-stained sections. The surface areas of each identifiable portal tract and those of the portal vein it contained were computed. Longitudinally cut portal tracts, those with surface areas greater than 0.5 mm2 and those with no recognizable bile ducts were excluded. After establishing a ratio portal vein area (PV)/portal space area (PSI for each case, we determined a mean ratio. These surface areas were then classed into three categories (class 1 < 0.04 mm2, class 2 > 0.04 < 0.17 mm2, class 3 > 0.17 mm2), and a mean PVPS ratio was calculated for each.

Statistics:

Results were expressed as mean ± S.D. and statistically compared with the control group with an ANOVA test for repeated measurements (p < 0.05).

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Description (incidence and severity):

only temporarily affected

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
- No mortality was observed in animals fed 2 or 4 ppm in the diet.

BODY WEIGHT AND WEIGHT GAIN
- Growth depression occurred during the first 2 weeks in animals of the 4 ppm group; final body weight was not significantly affected.
- Rats of the 2ppm grew normally.

CLINICASL CHEMISTRY
- Liver function (total bilirubin; AST, ALT, AP and GGT) was in the control range for both groups.

ORGAN WEIGHTS
- Slight but significant increase in liver weight (absolute and related to body weight) was observed in the 4 ppm but not the 2 ppm group.
- Spleen weights were not significantly increased.

GROSS PATHOLOGY
- Gross pathological changes were observed in livers of the 4 ppm animals: atrophic micronodular, reddish lobes with occasionally clearly visible veins on the surface alongside other changes including hypertrophy with only a slight irregular surface.

HISTOPATHOLOGY:
- In the 4 ppm group, atrophic lobes displaying a peripheral nodular zone with micronodules separated by rows of atrophic hepatocytes without fibrosis, characteristics of nodular regenerative hyperplasia, and a central atrophic zone that was sometimes peliotic.
- Hypertrophic lobes and livers in the less severe cases (4 ppm) had only minor and relatively localised evidence of nodular regenerative hyperplasia; occasionally peliosis was seen.
- In all cases (4 ppm), portal veins, hepatic veins and arteries were normal; by electron microscopy, in nodular zones with no obvious evidence of parenchymal atrophy, the endothelial wall showed signs of complete or incomplete capillarization with frequent enlargement of the Disse space.
- Only minor and inconsistent changes were observed at 2ppm.

OTHER FINDINGS
- No obvious signs of clinical hypertension, but portal pressure increased by a factor of 1.8 in the 4 ppm group.

Effect levels

Dose descriptor:

NOAEL

Effect level:

0.12 mg/kg bw/day (nominal)

Based on:

element

Remarks:

Se

Sex:

male

Basis for effect level:

gross pathology

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Based on effects on liver weights, gross and histopathological findings observed at 4 ppm (0.24 mg Se/kg bw/d), the NOAEL for hepatotoxicity can be established at the lower dose level of 2 ppm selenium (0.12 mg Se/kg bw/d) in the diet.