Evolution of 3-hydroxy-3-methylglutaryl-CoA reductase and microsomal membrane fluidity throughout chick embryo development

Abstract

1. 1. The pattern of chick liver and brain 3-hydroxy-3-methylglutaryl-CoA reductase and its relationship with changes in microsomal membrane fluidity was studied during embryonic and postnatal development. 2. 2. A peak of brain activity was found at 19 days of embryonic development, while liver activity only increased after hatching. 3. 3. A significant increase in cholesterol content of brain microsomes ocurred at about 14 days of incubation, decreasing afterwards. No significant variations were observed in liver microsomes during the same period. 4. 4. A similar profile was found in the phospholipid content of both brain and liver microsomes. 5. 5. The cholesterol/lipidic phosphorus molar ratio of brain and liver microsomes did not exhibit significant changes throughout embryonic and postnatal development. 6. 6. These results demonstrate that membrane-mediated control does not regulate the evolution of reductase activity during this developmental period.