Effects of Reduced Maternal Lipoprotein-Cholesterol Availability on Placental Progesterone Biosynthesis in the Baboon

Maternal low density lipoprotein (LDL) is the principal source of cholesterol substrate for progesterone biosynthesis in the primate placental syncytiotrophoblast. The relationship of LDL-cholesterol availability and other potential cholesterol-yielding pathways to placental progesterone production have not, however, been demonstrated in vivo in a nonhuman primate. Therefore, maternal peripheral lipoprotein-cholesterol and progesterone concentrations were determined in blood samples obtained by venipuncture, from day 72 until day 100, from pregnant baboons (Papio sp) that were either untreated (n = 4) or treated (n = 3) with the inhibitor of hepatic lipoprotein production, 4-aminopyrazolo[ 3–4-d]pyrimidine (4-APP, 10 mg/kg BW) on days 98–99 of pregnancy (term = 184 days). Although LDL-cholesterol and progesterone levels remained unchanged in untreated animals, LDL-cholesterol concentrations were 9-fold lower (P < 0.005) in baboons receiving 4-APP than in untreated baboons 2 days following initial administ...