Effect of substrates and of coronary artery ligation on mechanical performance and on release of lactate dehydrogenase and creatine phosphokinase in isolated working rat hearts.

Glucose and fatty acid substrates had different effects on the cardiac output, heart work and rates of release of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) from isolated perfused working rat hearts with coronary artery ligation. Release of LDH or CPK was increased in hearts perfused with free fatty acids (FFA) instead of glucose. The addition of insulin decreased palmitate-induced release of LDH but did not increase cardiac output, while the addition of glucose to hearts perfused with fatty acid both increased cardiac output and depressed LDH release. In FFA-perfused hearts addition of both glucose and insulin gave lowest rates of enzyme release and increased cardiac output, heart rate and heart work. It is proposed that glucose and/or insulin protected the hearts from the deleterious effects of FFA.