Different developmental patterns of 3-hydroxy-3-methylglutaryl-CoA reductase in chick tissues according to their role in cholesterogenesis.

The developmental pattern of microsomal 3-hydroxy-3-methylglutaryl-CoA reductase activity was different in liver, intestine and brain of neonatal chicks. Hepatic reductase activity sharply increased between 5 and 9 days after hatching. This pattern agrees with changes in acetate incorporation into non-saponifiable lipids by liver slices. Both enzyme activity and acetate incorporation seem to be related to the hepatic uptake of cholesterol from the yolk sac during the first days after hatching and to the new synthesis of cholesterol commencing in the second week. Changes in intestinal reductase suggest that the enzyme was less sensitive to the cholesterol in yolk sac. Brain reductase did not change within the age assayed (1-15 days), being independent from the levels of yolk sac or serum cholesterol during the later steps of myelination.