Progesterone metabolism in human endometrial stromal and gland cells in culture

Metabolism of progesterone by human endometrium has been described, but the rapidity and extent of progesterone metabolism is incompletely documented in cellular fractions of normal endometrium. Therefore, we evaluated progesterone metabolism in separated stromal and gland cells in culture obtained from normal human endometrium by thin-layer chromatography. We find that in both cell types, the most abundant metabolite is 3beta-hydroxy-5alpha-pregnan-20-one (70%), followed by 5alpha-pregnane-3,20-dione (15%), and 3alpha-hydroxy-5alpha-pregnan-20-one (10%). A small amount is metabolized to 5alpha-pregnane-3alpha/3beta,20alpha-diols and to 3beta,6alpha-dihydroxy-5alpha-pregnan-20-one. The metabolism of progesterone in cultured endometrial cells occurs rapidly; 70% of progesterone is metabolised in 8 h, and 90% by 24 h. We conclude that when in vitro experiments are conducted utilizing progesterone treatment, the rapidity and the extent of the metabolism of this steroid should be taken into account.