EFFECTS OF HEALTHY PSEUDOPREGNANT MILIEU ON DEVELOPMENT OF 2-CELL SUBDIABETIC MOUSE EMBRYOS

Female mice were injected with a single dose of streptozotocin (65 mg kg(-1)) 14-17 days before fertilization to investigate the significanc e of impaired insulin secretion induced by subdiabetic streptozotocin treatment on preimplantation embryo development. Subdiabetic mice (str eptozotocin-treated) had significantly different glucose tolerance fro m that of control animals, despite similar basal glycaemia. Morphologi cal analysis of preimplantation embryos collected on day 2 of pregnanc y revealed no significant changes in the number of two-cell embryos re covered from streptozotocin-treated females compared with controls. Tw o-cell embryos were transferred into the oviducts of healthy, synchron ous pseudopregnant females and recovered 24-28 h later. Morphological evaluation revealed a significantly greater percentage of degenerated embryos from streptozotocin-treated females than from control females. Morphological analysis of preimplantation embryos collected on day 2. 5 of pregnancy revealed no significant changes in the number of two- t o four-cell embryos recovered from streptozotocin-treated females comp ared with controls, but there was a significant increase in the number of degenerated embryos in streptozotocin-treated females that did not receive insulin therapy. Insulin (1-1.5 iu per 100 g) administered tw ice a day to streptozotocin-treated mice significantly improved the al tered development of embryos in both experiments. It is possible that the impaired insulin secretion in female mice adversely affected the g rowth of preimplantation embryos. Almost half of the morphologically n ormal two-cell embryos isolated from subdiabetic females were incapabl e of development to the eight-cell stage even in a non-diabetic matern al environment. The morphologically distinct degenerative changes were first detected at the time of the second mitotic cleavage.