EMBRYONIC LOSSES AFTER 10-WEEK ADMINISTRATION OF COBALT TO MALE-MICE

Cobalt toxicity was evaluated in the dominant lethal assay (DLA) to de termine whether the detrimental effects of cobalt on spermatozoa would have an impact on offspring. Male B6C3F1 mice were treated with cobal tous chloride (400 ppm Co) for 10 weeks and mated. Neither the stage n or rate of development in vitro of 2-cell embryos to blastocyst from c obalt-treated males was affected. There was an increase in preimplanta tion 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 perio d, decreased during the DLA, and recovered over the next 6 weeks. Sper m parameters at the end of DLA and the recovery period showed that cob alt decreased all parameters measured at 12 weeks, but these parameter s, except concentration, recovered to control levels by 18 weeks. Tiss ue concentrations of cobalt measured by atomic absorption analysis wer e increased in liver, kidney, testis, and epididymis after 12 weeks of cobalt treatment. We conclude that cobalt affected preimplantation lo sses in the DLA by compromising the fertility of treated males.