Teratogenic effects of tolbutamide on early-somite mouse embryos in vitro.

The present study investigated the teratogenicity of the oral hypoglycemic agent, tolbutamide, using an in vitro approach, and evaluated the role of its main metabolic effect, hypoglycemia. Teratogenesis was evaluated by culturing early-somite mouse embryos for 24 h in serum from rats treated with tolbutamide (79-117 micrograms/ml) or normal rat serum supplemented with tolbutamide (110-152 micrograms/ml). Tolbutamide-treated serum was then supplemented with glucose to control for potential effects of hypoglycemia. Mouse embryos demonstrated high malformation rates following exposure to serum from tolbutamide-treated rats (79%) or normal rat serum supplemented with tolbutamide (85%) compared with controls (4%), and defects included cardiac, ocular, neural tube, and somite abnormalities. Overall growth was reduced in treated embryos and yolk sacs, as determined by total protein contents. Embryonic growth and malformation rates were not improved by glucose supplementation of hypoglycemic tolbutamide-treated serum. Thus, tolbutamide produces malformation in mouse embryos in vitro at concentrations comparable to those in human serum, and the effects do not appear to be mediated by hypoglycemia. The potential risk of tolbutamide on the developing embryo must be considered in the therapy of pregnant diabetic patients.