Embryopathic effects of short-term exposure to hypoglycemia in mouse embryos in vitro

The effect of short-term hypoglycemia was studied at two stages of development in postimplantation mouse embryos in vitro. Day 8 (gastrulating) mouse embryos were placed in hypoglycemic medium (60, 80, 100, or 110 mg/dl glucose) for 4 hours in which normoglycemia (120 to 150 mg/dl glucose) was restored for the remaining 44 hours of culture. Day 9 (neurulating) mouse embryos were exposed to hypoglycemia (20, 40, 60, or 80 mg/dl glucose) for 2, 4, 6, or 24 hours followed by normoglycemia for the remainder of 24 hours. At the end of culture embryos were evaluated for growth and malformations and compared with controls grown in normoglycemic medium. The results show that a 50% reduction in glucose for as little as 2 hours causes dysmorphogenesis in neurulating mouse embryos, whereas longer exposure times, more severe levels of hypoglycemia, or both are required to affect growth. Furthermore, gastrulating embryos are more sensitive to short periods of hypoglycemia than those undergoing neurulation.