Effects of impaired insulin secretion on the fertilization of mouse oocytes

We have studied the effect of moderately impaired maternal insulinsecretion on oocyte chromosomal constitution, fertilizationand zygote DNA synthesis. Female mice were injected with a singledose of streptozotocin (65 mg/kg) 14 days before fertilization/ovulation.Zygotes/oocytes were recovered from control and subdiabeticmice on day 1 of pregnancy. Compared with control animals, subdiabeticfemales showed a significant difference in the proportion ofzygotes/oocytes. The subdiabetic mothers had a lower percentageof zygotes and a higher percentage of unfertilized and degeneratedoocytes in comparison with control animals. The investigationof [³H]thymidine incorporation did not show any influence ofthe maternal subdiabetes on the initial zygote DNA synthesis.An analysis of the ovulated oocytes at the metaphase II stageisolated from subdiabetic mice did not reveal increased chromosomalanomalies in comparison with the controls. Control and subdiabeticmothers had a similar percentage of oocytes with a normal haploidset of chromosomes, and the incidence of aneuploidy/diploidydid not differ significantly. These observations suggest thatinsulin changes in subdiabetic mothers had a deleterious influenceon oocyte fertilization in mice, but apparently they did nothave any effect on the nuclear events.