Cromakalim: Embryonic effects and reduction of tolbutamide-induced dysmorphogenesis in vitro

Cromakalim is a K+ channel opener that causes smooth muscle relaxation by a ctivating ATP-sensitive K+ (K-ATP) channels and producing membrane hyperpol arization. Cromakalim counteracts sulfonylurea-induced KATP channel inhibit ion in adult cells, but lime is known regarding its embryonic effects, alon e or in combination with sulfonylureas. KATP channels have been demonstrate d in the embryo, but their role in normal and abnormal development is unkno wn. Early-somite mouse embryos were exposed for 24 hr in vitro to cromakali m at concentrations of 0 (Cntl), 1, 10, 100, 200, or 500 mu M in 0.125% DMS O. Embryos were also exposed for 24 hr in vitro to a dysmorphogenic tolbuta mide concentration (110 mu g/ml) combined with a subdysmorphogenic concentr ation of cromakalim (1 mu M). Embryos were evaluated for somite number, hea rt rate, malformations, and embryonic and yolk sac protein content. Embryos exposed to 1 mu M cromakalim were similar to controls. Cromakalim exposure increased malformation rates at concentrations greater than or equal to 20 0 mu M, decreased heart rates at greater than or equal to 10 mu M, and decr eased somite and protein Values at 500 mu M. Defects involved cranial neura l tube, optic vesicle, heart, and somites. A malformation rate of 59% in em bryos exposed to 110 mu g/ml tolbutamide was reduced to 13% by adding 1 mu M cromakalim to the culture medium. Heart rate, somite number, and protein values were also improved by combined exposure to cromakalim and tolbutamid e compared with exposure to tolbutamide alone. These results support previo us findings with diazoxide (K+ channel opener) and chlorpropamide (sulfonyl urea) and further suggest a potential role for KATP channel effects in sulf onylurea-induced dysmorphogenesis. (C) 1999 Wiley-Liss, Inc.