[Functional interrelationship between granulosa and theca lutein cells in steroidogenesis in vitro by human corpus...

To investigate the interrelation between steroidogenic function of granulosa and theca lutein cells of the human corpus luteum, twelve corpora lutea of menstruation and pregnancy were divided into inner and outer layers, each of which was histologically confirmed to be composed of pure granulosa lutein cells (GL) or GL plus theca lutein cells (TL), respectively. Slices of each layer were incubated with radioactive pregnenolone, 17-hydroxyprogesterone and androstenedione respectively, and the metabolites were analysed by reverse dilution technique with recrystallization to constant specific activity. Both slices converted pregnenolone-14C to progesterone, 17-hydroxyprogesterone, androstenedione, estrone and estradiol-17 beta, with progesterone being the major steroid formed. Formation of progesterone was significantly pronounced in the case of slices from the inner layer, while conversion into the other steroids was significantly higher in the case of slices from the outer layer. Formation of androstenedione from 17-hydroxyprogesterone-14C was also greater with the outer slices than the inner slices. However, conversion of androstenedione-14C to radioactive estrone and estradiol-17 beta was more efficient with the inner slices than the outer slices. These results suggest that the activity of aromatizing enzymes is higher in granulosa lutein cells, while that of 17 alpha-hydroxylase and C17-C20 lyase is higher in theca lutein cells. Therefore, cooperation of the two cell types would be necessary for the fulfillment of the function of estrogen biosynthesis by human corpus luteum.