Cellular necrosis in zinc-deficient rat embryos.

Abnormal cellular necrosis was studied in 9.5-11.5-day embryos obtained from zinc-deficient rats. At periods of low maternal zinc status induced by a high intake of a zinc-deficient diet, cell death was observed in those regions of the embryo that were most sensitive to teratogenic insult at that time. As the maternal serum zinc level increased during the fasting phase of the feeding cycle, the degree of necrosis decreased, leaving the tissue histologically more normal even though the embryos were grossly malformed. The mitotic index of cells in the neural epithelium and limb buds of zinc-deficient, non-necrotic embryos was found to be elevated, but there was no evidence of blockage at any particular stage of mitosis. It can be hypothesised that during the early stages of organogenesis, periods of low maternal zinc status initiate unscheduled cell death by some as yet undefined mechanism that in turn, gives rise to the morphological anomalies observed later.