Carnitine palmitoyltransferase activity and fatty acid oxidation by livers from fetal and neonatal rats

Abstract

In liver preparations from fetal rats, the rate of palmitate oxidation to CO₂ was approximately one-tenth that found in adult liver homogenates, and the rate of incorporation of labeled palmitate into acetoacetate by livers from fetal animals was approximately one-hundredth of the corresponding rate in liver preparations from neonatal rats. Shortly after birth, the hepatic rate of oxidation of long-chain fatty acids increased greatly, and in liver preparations from 2-day-old rats, the rate was faster than that observed in adult liver preparations.The changes in activity of carnitine palmitoyltransferase in hepatic mitochondria from fetal and neonatal rats were nearly parallel to changes in fatty acid oxidation. Activities in fetal liver preparations were approximately one-tenth those observed in liver mitochondria from adults, while activities in hepatic mitochondria from 2- or 3-day-old rats were slightly greater than those found in adult liver.It was concluded that the rate of hepatic fatty acid oxidation in fetal and neonatal rats, as well as in adult animals, is influenced by the levels of carnitine palmitoyltransferase activity. The possible regulatory role of carnitine and the carnitine palmitoyltransferase reaction in fatty acid oxidation is discussed.