Gonadotropin- and lipoprotein-supported progesterone production by primate luteal cell types in culture

This study examined the ability of gonadotropin and lipoproteins to support progesterone (P) production during long-term culture of luteal cell types obtained from rhesus macaques at midluteal phase of the menstrual cycle. Mixed (unsorted) luteal cells and small and large cells sorted by flow cytometry were cultured with human IDL, acetylated (ac)LDL or high density lipoprotein (HDL) (0-100 μg protein/ml) with or without hCG (100 ng/ml). In mixed cells, daily P levels declined during culture, although treatment with hCG alone increased P levels on all days of culture. Treatment with LDL, acLDL or HDL alone had no effect on P levels. However, hCG + LDL sustained P levels through day 4 at or above day 1 control values. Treatment with hCG + acLDL also increased P production above that of hCG alone, but hCG + HDL only modestly enhanced P production (180%). Although hCG stimulated P production by freshly-harvested large, but not small, cells during acute (3h) incubation, both cell types responded to hCG with up to an eightfold increase in P production on days 1-4 of culture. P levels were essentially nondetectable in both sorted cell groups by day 4. Small cells did not respond to any of the three lipoprotein treatments; large cells responded to LDL or acLDL on day 1, but this response was not apparent later in culture. Treating small or large cells with hCG + lipoprotein was no different from hCG alone. Thus, (1) LDL, and to some extent modified LDL, supports gonadotropinstimulated steroidogenesis by mixed cell populations in the monkey corpus luteum; (2) the lack of LDL response by sorted cell types suggests that the culture conditions or absence of other cell types renders lipoprotein treatment ineffective; and (3) small luteal cells develop the cellular components necessary for gonadotropin-stimulated steroidogenesis within 24 h of culture.