Plasma lipoproteins stimulate progestin production by rat ovarian granulosa cells cultured in serum free medium

Abstract

Abstract These studies investigated the effect of human high density lipoprotein (hHDL), human low density lipoprotein (hLDL), and rat high density lipoprotein (rHDL), on steroidogenesis by cultured rat ovarian granulosa cells. Granulosa cells were isolated from ovaries of estrogen stimulated, hypophysectomized, immature female rats, and were cultured in a serum-free medium. After pretreatment of the cells in culture for 2, 4, or 6 days with oFSH and 4-androstene-3,17-dione to induce the enzymes necessary for progestin synthesis, the addition of hHDL to the cultures for 2 days resulted in a 4 to 6 fold increase in granulosa cell progesterone and 20α-hydroxy-4-pregnen-3-one production. The predominant progestin was 20α-hydroxy-4-pregnen-3-one and maximum progestin production occurred after 4 days of oFSH and 4-androstene-3,17-dione pretreatment. Dose-response studies showed that progestin production was linear with the log dose of hHDL. The addition of hLDL and rHDL for 2 days also stimulated a 2 to 4 fold increase in progesterone and 20α-hydroxy-4-pregnen-3-one production by granulosa cells pretreated for 2 days with oFSH and 4-androstene-3,17-dione. In contrast to their stimulatory effect on progestin synthesis, the lipoproteins had no effect on granulosa cell estrogen production. These results demonstrate that rat and human plasma lipoproteins act directly on granulosa cells to stimulate progestin production, presumably by providing cholesterol substrate. The granulosa cell culture system utilized in this report permits the study, under controlled conditions, of the role of plasma lipoproteins in rat ovarian steroidogenesis.