Fetal aortic cholesterol concentration and metabolism: relationship to plasma cholesterol and potential role of placental factors

Abstract

The relationship of fetal plasma cholesterol levels to aortic free and esterified cholesterol concentration was determined in the rabbit during gestation. Plasma cholesterol levels (mg/dl) in early fetuses were markedly high and decreased at term. While aortic free cholesterol content increased with fetal age, cholesteryl ester concentration did not change significantly and no pathological accumulation was evident. This occurred despite high fetal aortic cholesterol esterification activity noted in earlier studies. We evaluated the potential effect of rabbit placental extracts on lipid metabolism and cellular proliferation in fetal aortic explants to explore the role of placental factors in affecting lipid metabolism. Labeled [ 14C]oleate and [ 3H]thymidine were used to investigate the rates of incorporation of (a) oleate into lipids, and (b) thymidine into DNA, respectively. Placental extracts at term (but not from 22 days gestation) significantly decreased oleate incorporation ( P < 0.05) into cholesteryl esters, phospholipids and diglycerides. This effect of placental extracts was noted both in absence or presence of serum in the culture medium, and was predominantly found in fraction of M r > 100 000. [ 3H]Thymidine incorporation (dpm/g protein) into DNA was significantly decreased ( P < 0.01) by placental extracts. These studies suggest that placental extracts contain factor(s) influencing fetal aortic lipid metabolism in culture.