Differential effects of hypoxia on electrical and mechanical activities of isolated ventricular muscles from fetal and adult guinea-pigs.

1. Effects of hypoxia (95% N2 + 5% CO2) and cromakalim (30 microM) on mechanical and electrical activities of isolated ventricular muscles were examined in fetal and adult guinea-pigs. 2. Hypoxia markedly reduced both the action potential duration (APD) and the contractile force (CF) in the adult, which was only partially restored by 10 microM glibenclamide, while it only slightly reduced CF with little affecting APD in the fetus. 3. Cromakalim markedly reduced both APD and CF in both age groups similarly. 4. Thus, we demonstrated that APD and CF of fetal ventricular muscles are resistant to hypoxia as compared with those of adult. This may be explained by difference in metabolic pathways rather than by lack of ATP-sensitive potassium channels.