Embryonic losses after 10-week administration of cobalt to male mice

Cobalt toxicity was evaluated in the dominant lethal assay (DLA) to determine whether the detrimental effects of cobalt on spermatozoa would have an impact on offspring. Male B6C3F1 mice were treated with cobaltous chloride (400 ppm Co) for 10 weeks and mated. Neither the stage nor rate of development in vitro of 2-cell embryos to blastocyst from cobalt-treated males was affected. There was an increase in preimplantation losses and a decrease in total and live births, but no change in postimplantation losses from litters at day 19 of gestation. Fertility of the males was maintained during the 10-week cobalt treatment period, decreased during the DLA, and recovered over the next 6 weeks. Sperm parameters at the end of DLA and the recovery period showed that cobalt decreased all parameters measured at 12 weeks, but these parameters, except concentration, recovered to control levels by 18 weeks. Tissue concentrations of cobalt measured by atomic absorption analysis were increased in liver, kidney, testis, and epididymis after 12 weeks of cobalt treatment. We conclude that cobalt affected preimplantation losses in the DLA by compromising the fertility of treated males.