Evidence for cleavage of [26-14C]cholesterol side-chain by human foetal membranes in vitro

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Abstract
With a view to establish the hitherto undescribed role of cholesterol in fetal-membranous steroidogensis, homogenates of term chorion pars reflexa and amnion pars reflexa and pars placentaris collected from 6 women after spontaneous labor at term (38-41 wk gestation) were incubated with [26-14C]cholesterol. Using reverse-isotope dilution analysis [14C] isocaproic acid was isolated and characterized. This conversion constitutes strong evidence that C-20, 22-desmolase activity, normally present in the adrenal, gonadal and placental tissues, is present in the homogenates of both membranes. Efficiency of the enzymic conversion suggests that the chorion possesses a more active desmolase system than that of the amnion.