Androgen and FSH synergistically stimulate lipoprotein degradation and utilization by ovary granulosa cells

Abstract

Androgen can directly modulate the induction of steroidogenic enzymes by FSH (follicle stimulating hormone) in ovary granulosa cells. In studies of its mechanism of action, we examined the androgen effect on granulosa cell interaction with lipoproteins, the physiologic source of cholesterol. After granulosa cells were cultured for 48 hours with and without androgen and/or FSH, the cells were incubated for 24 hours with 125I-lipoproteins [human high density lipoprotein (HDL), rat HDL, or human low density lipoprotein (LDL)]. The media were then analyzed for lipoprotein protein coat degradation products (mainly 125I-monoiodotyrosine) and progestin [mainly 20α-dihydroprogesterone (20α-DHP)]. In the absence of FSH and androgen, 2 × 10 5 granulosa cells degraded basal levels of all three lipoproteins, but produced no measurable 20α-DHP. The addition of 10 −7 M androstenedione (A), testosterone (T), or 5α-dihydrotestosterone (DHT) had no effect on lipoprotein protein degradation or 20α-DHP production. FSH alone stimulated lipoprotein protein degradation by 50 to 300% while the addition of androgen synergistically augmented the FSH-stimulated 20α-DHP production as well as protein coat degradation of all three lipoproteins. DHT and T were both effective, indicating that androgens themselves, and not estrogen products, were responsible for the effect on lipoprotein protein degradation and 20α-DHP production. The addition of a 10-fold excess cyproterone acetate (an anti-androgen) inhibited the effect of T, suggesting that the action of T was mediated by the granulosa cell androgen receptor. Androgen and FSH also synergistically stimulated the production of 3H-progestin when the granulosa cells were incubated with either 3H-cholesterol ester core labeled human HDL or similarly labeled human LDL. This report demonstrates that androgen, in combination with FSH, augments the steroidogenic pathway of the granulosa cell from the degradation of lipoprotein and utilization of the cholesterol ester core, to the production of progestin product.