Cobalt(2+) hydrogen citrate

Toxicity to reproduction: other studies

Administrative data

Endpoint:

toxicity to reproduction: other studies

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Basic data given.

Data source

Reference

Reference Type:

publication

Title:

Embryonic Losses after 10-week Administration of Cobalt to Male Mice

Author:

Pedigo, N.G. and Vernon, M.W.

Year:

1993

Bibliographic source:

Reproductive Toxicology 7: 111-116

Materials and methods

Principles of method if other than guideline:

Male mice are treated with the test substance via drinking water and are mated with untreated female at different time points of the administration period.
- In a dominant lethal assay (DLA) male mice that were treated with cobalt for 10 weeks are mated with untreated females for 2 weeks. To assess the impact of subchronic cobalt administration on offspring. Pregnant female are sacrificed on day 19 of gestation and the foetuses are evaluated as well as the number of resorption and number of preimplantation losses.
- Fertility after administration of cobalt is assessed by evaluating the growth and development of embryos in vitro (from 2-cell stage) at different administration time points as well as after a 8-week recovery period and by computerized semen analyses after the DLA (week 12).
Levels of cobalt in male reproductive tissue is determined after termination of the administration period and after the recovery period.

GLP compliance:

not specified

Type of method:

in vivo

Test material

Test material information

Constituent 1

Reference substance name:

cobalt chloride hexahydrate

IUPAC Name:

cobalt chloride hexahydrate

Constituent 2

Reference substance name:

7791-13-1

EC Number:

616-574-6

Cas Number:

7791-13-1

IUPAC Name:

7791-13-1

Details on test material:

- Name of test material (as cited in study report): cobalt chloride hexahydrate
- Analytical purity: no data

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Co., Indianapolis, IN, USA
- Age at study initiation: (males) 8-10 weeks; (females) 6-7 weeks
- Weight at study initiation: (mean) 26.32 ± 1.6 g
- Housing: (males) individually; (females) 5/cage
- Diet: Purina Rodent Chaw; ad libitum
- Water: ad libitum
Each male was required to produce 2 confirmed pregnancies within 2 weeks as a demonstration of reproductive competence.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23
- Photoperiod (hrs dark / hrs light): 10/14

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Remarks:

(from a Milli-Q Pyrogen Free Water System)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

10 weeks (only males were treated)

Frequency of treatment:

daily via drinking water

Duration of test:

18 weeks (including DLA (2 weeks) and additional recovery period of 6 weeks)

Doses / concentrations

Remarks:

Doses / Concentrations:
400 ppm
Basis:
nominal in water

No. of animals per sex per dose:

10 (males in DLA)

Control animals:

other: yes, pure drinking water

Details on study design:

Culture of preimplantation embryos:
The growth and development of preimplantation embryos from cobalt-treated males and untreated females (mated 1:1) was evaluated in vitro. Evaluation began 1 week after the beginning of cobalt administration to week 9. The pregnant females are sacrificed on day 2 of gestation for collection of ova/embryos and the growth and development of the embryos was evaluated in vitro. The number of 2-cell embryos with equal-sized blastomeres were counted as fertilized oocytes and the fertilization rate calculated as a percentage of total ova released. The embryos were evaluated daily from the 2-cell embryo to the blastocyst at 72 h.
Dominant lethal assay:
To study the potential importance of preimplantation losses, the effects of cobalt on the offspring of treated males were assessed in a dominant lethal assay (DLA). 10 control and 10 treated males were mated with untreated females over a period of 2 weeks after cobalt administration for 10 weeks (via drinking water). Pregnant females were sacrificed and autopsied on day 19 of pregnancy (vaginal plug detection is defined as day 1 of gestation). Fetuses were evaluated according to the following criteria: gross abnormalities, viability, and fetal size. The number of resorptions were counted and the number of preimplantation losses were calculated as the difference between the number of corpora lutea in the ovary and the number of total implants.

Evaluation of testicular function and sperm motion characteristics:
At the end of the DLA, 5 males of both groups were sacrificed and epididymal sperm were collected and evaluated to determine concentration, motility, path velocity, progressive velocity, linearity lateral head displacement, progressive motility and track speed to determine whether the administration of cobalt influences the function of mature spermotazoa.

Evaluation of fertilization and recovery:
At the end of the DLA, 5 males of both groups were maintained for 6 weeks for evaluation of recovery of fertility and corresponding sperm parameters. For evaluation they were mated (1:1, overnight) with untreated females.
Evaluations of fertility were performed after 7 and 10 weeks of treatment and after the DLA (12 weeks) and during recovery (weeks 16 and 18). Females were sacrificed on day 2 of gestation for collection of ova/embryos and the number of ova/embryos the percentage of fertilisation (2-cells or greater) was calculated.

Statistics:

- DLA: Student's t-test
- Fertility rate and fertilization rate: chi square analysis
- Development of preimplantation embryos: compartmental analysis
- Comparison of sperm parameters: computerized anaylsis using Student's t-test

Results and discussion

Effect levels

Dose descriptor:

LOAEL

Remarks:

reproduction

Effect level:

400 ppm (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: sperm parameters, effects on offspring

Observed effects

- Preimplantation embryonic growth and development in vitro: no effect

- Dominant lethal assay: The percentage of pregnant females (91% (control) vs. 58%, p < 0.001), the number of live embryos per female, and the number of preimplantation losses (0.43 (control) vs. 2.4, p < 0.001) per female were significantly changed in the cobalt-treated group.

- Testicular function and sperm motion characteristics: All sperm parameters were significantly depressed (week 12) except lateral head displacement. Sperm concentration was reduced to 15.3% of control values, motility at 18.3% , path velocity to 30.8%, progressive velocity to 22.2%, linear index to 75.7%, progressive motility to 17.2%, and track speed to 43.7% of control. After 18 weeks (recovery), all sperm parameter values had returned to control levels except concentration (recovered to 63.8% of control).

- Testicular weight: 12 week: 215 ± 24.5 mg (control) vs. 87.5 ± 5.9 mg; 18 week (recovery): 234.2 ± 14.4 mg (control) vs. 140.5 ± 8.7 mg

- Fertilization and recovery: During the 10 weeks of cobalt administration, there was no difference in the fertilisation rate between the groups. After the DLA mating was completed (week 12), the fertilization rate in the treated group was reduced to 1.8% as compared with a control rate of 82.4%. Over the next 4 weeks, the fertilization rate increased, but remained significantly below control values. After 8 weeks of recovery, the fertilization rate returned to control values.

- Cobalt accumulation in tissue: the concentration of cobalt was significantly elevated in renal tissue (224% over controls at the end of the DLA and 119% afte the 8-week recovery period). The hepatic concentration was 187.5% and 137% over control at 12 and 18 weeks, respectively. The concentration of cobalt in testis and epididymides was increased to 252% and 172% over control after 12 weeks, respectively, but the total amount of cobalt per testis and epididymides was unchanged as the tissue weight was significantly lower than that of controls at both 12 and 18 weeks.

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, it is concluded that cobalt affects preimplantation losses in the DLA by compromising the fertility of treated males.