The effect of cadmium on oogenesis in Xenopus laevis

Reproductive toxicity studies have historically centered on post-fertilization events. A thorough assessment of reproductive hazards to an organism should include all aspects of its life cycle. Cadmium is a teratogenic and carcinogenic heavy metal that occurs naturally in the environment but is also released anthropogenically. The effect of cadmium administration on oocyte development in Xenopus laevis was studied. Adult female Xenopus were injected in the dorsal lymph sac with cadmium chloride (CdCl2) at doses of 0.5, 0.75, 1.0, 3.0 or 5.0 mg/kg every other day for 21 days. Significant adverse effects of Cd on oocyte development were observed. The percentage of oocytes at all stages of oogenesis was decreased while the population of atretic oocytes increased dramatically (P < 0.0001). Numerous oocytes exhibited a speckled or mottled appearance and the incidence of completely atretic oocyte follicles increased. The observations indicate that Cd has the potential to significantly disrupt oogenesis and that examination of developing gametes may be a useful parameter for assessing the influence of environmental contaminants on reproductive capacity.