Effects of healthy pseudopregnant milieu on development of two-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 significance of impaired insulin secretion induced by subdiabetic streptozotocin treatment on preimplantation embryo development. Subdiabetic mice (streptozotocin-treated) had significantly different glucose tolerance from that of control animals, despite similar basal glycaemia. Morphological analysis of preimplantation embryos collected on day 2 of pregnancy revealed no significant changes in the number of two-cell embryos recovered from streptozotocin-treated females compared with controls. Two-cell embryos were transferred into the oviducts of healthy, synchronous 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- to four-cell embryos recovered from streptozotocin-treated females compared 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 twice a day to streptozotocin-treated mice significantly improved the altered development of embryos in both experiments. It is possible that the impaired insulin secretion in female mice adversely affected the growth of preimplantation embryos. Almost half of the morphologically normal two-cell embryos isolated from subdiabetic females were incapable of development to the eight-cell stage even in a non-diabetic maternal environment. the morphologically distinct degenerative changes were first detected at the time of the second mitotic cleavage.