Effects of hypophysectomy and corticosterone acetate treatment on hepatic lipid composition in the chick (Gallus domesticus) embryo.

Lipid is transferred from yolk to liver and to other tissues at an accelerated rate after 16 days of incubation in the intact chicken embryo. Hypophysectomy (partial decapitation) at 36 hr of incubation reduced liver lipid content on Days 16 and 18. The greatest losses on Day 18 were among cholesterol esters but decreased unesterified cholesterol and phospholipid were also observed. Treatment of hypaph-ysectomized embryos with corticosterone acetate (300 pg per day on Days 13, 14, 15) partially restored total hepatic lipid content to control values on Day 16, with an even greater effect on 18 days of incubation. Most of the increase in lipid occurred in the triglyceride fraction. Liver cholesterol content also increased in response to hormone but neither cholesterol esters nor phospholipids were elevated by corticosterone acetate. Hypophysectomy interferes with the absorption of lipids from yolk and with fat deposition in embryonic liver. However, treatment of hypophysectomized embryos with corticosterone acetate did not correct the major defects in hepatic lipid content. Therefore, fat metabolism and transport of yolk lipids to the embryo during the last week of incubation does not depend exclusively on adrenal glucocorticoids.