Steroid Hormone Formation in the Human Ovary: V. Synthesis of Progesteronein Vitroin Corpora Lute a During the Reproductive Cycle

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Abstract
Progesterone synthesis in vitro and the influence of exogenous gonadotropin were studied in slices of 50 individual human corpora lutea removed at different times during the reproductive cycle. Radioactive progesterone synthesis (dpm) was assessed by incorporation of radioactivity from acetate-1-14C. The progesterone contained in corpora lutea and formed in vitro from endogenous precursors (μg) was measured spectrophotometrically by its absorption of ultraviolet light. All luteal phase corpora lutea synthesized progesterone in vitro as measured by these 2 parameters (dpm and μg). No radioactive progesterone synthesis (dpm) from acetate-1-l4C was found in 3 corpora lutea obtained after onset of menses, although 2 of the 3 specimens synthesized progesterone (μg) from endogenous precursors. Corpora lutea from all phases of pregnancy and up to 4 days post partum synthesized progesterone in vitro. The capacity for steroid biosynthesis during the post-par turn period appeared to decline gradually when steroidogenesis by post-partum corpora lutea was compared with the specimens obtained during pregnancy or at term. Corpora lutea of pregnancy, as a group, formed progesterone of higher specific activity (dpm/μg) than corpora lutea of the menstrual cycle by utilizing acetate-1-14C more efficiently (dpm/g of tissue) and forming less progesterone from endogenous precursors (μg/g of tissue). The biochemical differences between corpora lutea of the cycle and pregnancy measured in vitro appear to reflect the different hor monal milieu to which the corpora lutea were exposed in vivo.

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