Evidence for de novo Cholesterol Synthesis by Term Human Fetal Amnion and Chorion: A Comparative Study Using the Reverse-Isotope Dilution Technique

Abstract

The cholesterol biosynthetic activity was assessed using [2-¹⁴C]-acetate as substrate in the homogenates of amnion and chorion obtained from women (n = 6, age 26–39 years) after spontaneous labour at term (37–40 weeks of gestation) having uncomplicated pregnancies. Reverse-isotope dilution analysis gave positive identification of [¹⁴C]-cholesterol acetate in all incubations of viable tissues. This metabolite was not evident in heat-denatured homogenates which served as controls. The extent of enzymic conversion for amnion at 2.6 × 10^–3 to 0.19% was persistently higher than that of the chorion at 1.7 × 10^–3 to 9.0 × 10^–3%. The results indicate that human term fetal membranes possess the full complement of enzymes to catalyze the transformation of acetate to cholesterol. This study provides evidence that fetal membranes possess the capacity for de novo cholesterol biosynthesis, the sterol being essential for steroidogenesis as well as in embryo viability during pregnancy.