Prolactin and gonadotrophin interactions on progesterone formation in cultured human granulosa cells

Human granulosa cells were isolated from preovulatory follicles during cycles stimulated with HMG-HCG or clomiphene-HMG-HCG or from unstimulated cycles. The cells were cultured for 6-8 days in medium M199 containing fetal calf serum under 5% CO2 in air. Highly purified human prolactin and human chorionic gonadotrophin were added alone or in combination to the cultures, and the content of steroids in the medium was measured every second day, utilizing conventional RIA techniques. In the presence of HCG the formation of progesterone (P) increased 3-5-fold over the control level with maximal effect after 4 days. In cells derived from clomiphene-HMG-HCG stimulated cycles, prolactin per se did not influence basal P formation but reduced the stimulatory effect of HCG. This was only seen in granulosa cells from follicles greater than 20 mm in diameter. In experiments with Forskolin, an adenylate cyclase activator, P formation was stimulated and the stimulation was counteracted by the concomitant presence of prolactin, indicating that prolactin did not interfere with the LH-HCG receptor. In cells from smaller follicles, or in cells from follicles aspirated from the natural cycle prior to the endogenous LH peak, P formation was stimulated by HCG but the addition of prolactin did not reduce this stimulatory effect. The results are discussed in relation to earlier reports on prolactin effects in vitro both on laboratory animals and human material.