Sodium selenite

Toxicity to reproduction

Administrative data

Endpoint:

fertility, other

Remarks:

based on test type (migrated information)

Type of information:

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

Adequacy of study:

supporting study

Study period:

no data

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

Report is not reliable, because the study was conducted in house rats captured from poultry houses, the low number of animals per group and because the results showed a very high variability between animals.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Effects of dietary selenium on differentiation, morphology and functions of spermatozoa of the house rat, Rattus rattus L.

Author:

Kaur, R.; Parshad, V.R.

Year:

1994

Bibliographic source:

Muta. Res. 309, 29-35

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study investigated the effects of ingestion of 2 ppm and 4 ppm selenium (as sodium selenite) in the diet by the house rat, Rattus rattus, for 5 weeks. Food consumption, body weight gain, testicular and cauda epididymidis weight, concentration, motility and percentage of live spermatozoa and morphology were examined.

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): sodium selenite
- Molecular formula (if other than submission substance): Na2SeO3
- Molecular weight (if other than submission substance): 172.95
- Substance type: technical product
- Physical state: solid
- Other: sodium selenite purchased from Romali, Bombay
No further information given.

Test animals

Species:

rat

Strain:

other: house rat, Rattus rattus

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: rats captured from poultry houses
- Age at study initiation: mature rats
- Diet (ad libitum): pellets of rat feed in crushed form (CPF) supplied by Lipton India Ltd., Calcutta
- Water: ad libitum
- Acclimation period: 7 - 10 days
No further information given.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: diet

Details on exposure:

DIET PREPARATION
- Pellets were crushed to ensure proper mixing of the required amount of selenium (as sodium selenite) in the food.
- Group 1: diet without addition of sodium selenite.
- Group 2: diet containing 2 ppm sodium selenite.
- Group 3: diet containing 4 ppm sodium selenite.

Details on mating procedure:

no mating performed

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no data

Duration of treatment / exposure:

5 weeks

Frequency of treatment:

daily

Details on study schedule:

not applicable

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
2 ppm Se as sodium selenite
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
4 ppm Se as sodium selenite
Basis:
nominal in diet

No. of animals per sex per dose:

six male rats per dose group

Control animals:

yes, plain diet

Details on study design:

no data

Positive control:

no data

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: in weekly intervals and on day 36 before necropsy

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

WATER CONSUMPTION: No data

No further information given.

Oestrous cyclicity (parental animals):

not applicable

Sperm parameters (parental animals):

- A portion of the testis was punctured to remove one or two pieces of seminiferous tubule which were placed on a glass slide in a drop of saline solution and covered with a coverslip. The coverslip was pressed delicately to puncture the tubule to release its fluid on the slide. The tubular fluid was mixed with eosin-nigrosine staining solution and kept at 37 °C for 20 min. Similarly, the cauda epididymidis fluid obtained by pressing both caudae after their incision in 0.5 mL saline solution was incubated at 37 °C for 5 min and a drop of this was stained with eosin-nigrosine staining solution at 37 °C for 20 min. Smears of both testicular and cauda epididymidis fluids were drawn on clean, grease-free slides, air-dried and mounted in DPX. Three slides of each rat were studied for morphological abnormalities in different regions of the elongated spermatids and spermatozoa respectively under the light microscope. From each slide, at least 100 spermatozoa were examined, that is about 300 spermatozoa/rat.
- Sperm concentration in millions/mL of each rat was determined from diluted cauda epididymidis fluid with a haemocytometer.
- Sperm motility was estimated by hanging drop method in whole number units from 0 to 4. Zero indicates total immobility and 4 indicates maximum perceived motility; motility less than 2 was considered abnormal.
- Percentage of live spermatozoa was estimated by observing 100-150 spermatozoa from a slide smeared with eosin-stained cauda epididymidis fluid of each rat. Spermatozoa stained pink with eosin were considered dead and transparent ones (unstained) were considered live.

Litter observations:

not applicable

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: all surviving animals were killed by using chloroform vapour on day 36.

GROSS NECROPSY
- no data

HISTOPATHOLOGY / ORGAN WEIGHTS
- Testes and caudae epididymides were dissected and weighed.

Postmortem examinations (offspring):

not applicable

Statistics:

Statistical significance of the differences between different parameters of control and treated rats was determined by Student’s t-test.

Reproductive indices:

not applicable

Offspring viability indices:

not applicable

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

not specified

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

not examined

Other effects:

not specified

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

effects observed, treatment-related

Reproductive performance:

not examined

Details on results (P0)

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
- A significant decrease in body weights was observed in the 2 and 4 ppm groups compared to the control during the first week of treatment.
- Body weights returned to original levels and were maintained during the subsequent 4 weeks of the study.

REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS)
Sperm differentiation:
- Treatment with 2 ppm over 5 weeks had no visible adverse effects on any stage of elongated spermatids in comparison to control.
- Several types of abnormalities on the midpiece region of their flagellum were observed at 4 ppm selenium in the diet.
- Abnormal spermatids also showed changes in refractivness of their midpiece, and a few spermatides with multiple abnormalities were found in the 4 ppm group.

Sperm morphology:
- A dose dependent effect of selenium on the morphology of cauda apididymis spermatozoa was observed in comparison to control.
- Percentage of abnormalities related to the midpiece region in the 2 ppm group were statistically significantly (about 3 %) more than in control rats (0.6 %).
- In the 4 ppm group, percentage sperm abnormalities were statistically significantly (about 23%) increased with a highly variable response in individual animals (10-67%).
- Abnormalities in the 4 ppm group were related mainly to the midpiece region, but a statistically significant increased percentage (about 1%) of multiple sperm abnormalities was seen as well (0.02 5 in control).
- Abnormalities were characterised by bending of the proximal, middle and distal parts of the midpiece and bifurcation of proximal midpieces. Bending of midpiece resulted in coiling or torsion of the proximal midpiece.

Sperm functions:
- Sperm concentrations in the cauda epididymis were significantly less in the 4 ppm group compared to the 2 ppm and control groups.
- Sperm motility was adversely affected in the 4 ppm group, but not in the 2 ppm group.
- Significantly and dose-related reductions in the percentage of live spermatozoa were observed in rats of the 2 and 4 ppm groups compared to control.
- Sperm function parameters showed a high variability between rats.

ORGAN WEIGHTS (PARENTAL ANIMALS)
- Testis and cauda epidiymis weights in relation to body weights decreased does dependently in the 2 and 4 ppm groups.

Effect levels (P0)

Dose descriptor:

LOAEC

Remarks:

(male fertility)

Effect level:

2 ppm (nominal)

Based on:

element

Remarks:

equivalent to 0.12 mg Se/kg bw/d

Sex:

male

Basis for effect level:

other: see 'Remark'

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

No information on compound intake is given. Therefore, dose levels in mg/kg bw/d are calculated by using a conversion factor 0.06 for adult male rats of 250 g. Thus, dose level of 0.12 and 0.24 mg/kg bw/d are estimated for the dose groups fed with 2 or 4 ppm Se in the diet group, respectively.

Calculation of LOAEL for ZnSeO3:

molar weight of Na2SeO3: 172.95 g/mol

molar weight ZnSeO3: 192.3672 g/mol

molar weight Se: 78.96 g/mol

--> 0.12 mg Na2SeO3 = 0.13 mg ZnSeO3 --> LOAEL (rat, oral) ZnSeO3 = 0.13 mg/kg bw/d

Applicant's summary and conclusion

Conclusions:

Ingestion of 2 and 4 ppm selenium as sodium selenite in the diet by house rats (Rattus rattus) for 5 weeks caused a dose-dependent reduction in body weight, testicular and cauda epididymis weights, concentration, motility and percentage of live spermatozoa with simultaneous increases in the percentage of abnormal forms. Based on these results, the lowest dose level of 2 ppm must be regarded as a low adverse effect level. This LOAEL corresponds to 0.12 mg Se/kg bw/d and can be recalculated to 0.13 mg/kg bw/d ZnSeO3.