Regulation of hepatic cholesterol synthesis from mevalonate in suckling and weaned rats

The conversion of mevalonic acid into total nonsaponifiable lipids (NSF) and digitonin precipitable sterols (DPS) by 5000 g liver supernatant fractions was compared in suckling and weaned rats. The incorporation of mevalonate into both NSF and DPS was low in fractions from suckling rats and very high in fractions from weaned rats. The results indicate that the activities of one or more of the enzymes catalyzing the conversion of mevalonate into squalene and squalene into cholesterol change after weaning and may act as regulatory step(s) for cholesterol synthesis in the livers of suckling rats. It is suggested that the reduced synthesis of cholesterol in the liver of suckling rats is caused by the cholesterol in the maternal milk, and the rapid rise in cholesterol synthesis after weaning is due in part to the dietary change accompanying weaning, and in part to an increased need for cholesterol by developing liver.