Functional and Structural Relationships in Steroidogenesis in Vitro by Human Corpora Lutea during Development and Regression*

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Abstract
To investigate the steroidogenic function of human corpora lutea, during the menstrual cycle, slices of seven corpora lutea obtained at various stages in the luteal phase were incubated with [l-14C]acetate; four of them were incubated with [4-14C]pregnenolone simultaneously. Incorporation or conversion of 14C radioactivity into progestins, androgens, and estrogens was assessed by a reverse dilution technique with recrystalliza-tion to constant specific activity. Distinct differences in function and morphology were observed before and after the completion of corpus luteum formation. In developing corpora lutea, 1) a marked increase in pro-gesterone formation from [14C]acetate, 2) a transient increase in androgen formation, including dehydroepiandrosterone, with a concomitant decrease in estrogen formation from the two precursors, and 3) degeneration, followed by disappearance of thecal cells, were observed. In mature and regressing corpora lutea, 1) a drastic decrease in progesterone formation from [(14)C]acetate, 2) an increase in estrogen in contrast to a decrease in androgen formation from the two precursors, 3) a clear differentiation of theca lutein cells, and 4) a more relatively pronounced transformation of pregnenolone to estrogen in regressing than in mature corpora lutea were found. We conclude that marked qualitative and quantitative changes in steroidogenic function are closely related to structural changes during corpus luteal development and regression.