Studies on the synthesis of cholesterol in the brain of the human fetus

Following the intravenous injection of a single dose of acetate-C 14 to women during early pregnancy, only negligible amounts of isotope could be detected in fetal brain cholesterol, but a significant incorporation of C 14 occurred in cholesterol isolated from the corpus luteum of pregnancy, fetal liver, and fetal adrenals. Neither cholesterol-C 14 synthesized in the fetal liver nor maternal plasma cholesterol-H 3 of dietary origin was taken up by the fetal brain in appreciable amounts. When glucose-C 14 was injected in the mother, the isotope was found in cholesterol isolated from the fetal brain and other fetal tissues but only negligible amounts were found in maternal tissues. The preferential utilization of glucose for the synthesis of fetal brain cholesterol emphasizes the significance of the "blood-brain barrier" which controls the movement of substances into and out of central nervous system tissue.