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

Human granulosa cells were isolated from preovulatory folliclesduring cycles stimulated with HMG-HCG or clomiphene-HMG-HCGor from unstimulated cycles. The cells were cultwed for 6–8days in medium M199 containing fetal calf serum under 5% CO₂in air. Highly purified human prolactin and human chorionicgonadotrophin were added alone or in combination to the cultures,and the content of steroids in the medium was measured everysecond day, utilizing conventional RIA techniques. In the presenceof HCG the formation of progesterone (P) increased 3–5-foldover the control level with maximal effect after 4 days. Incells derived from clomiphene-HMG-HCG stimulated cycles, prolactinper se did not influence basal P formation but reduced the stimulatoryeffect of HCG. This was only seen in granulosa cells from follicles< 20 mm in diameter. In experiments with Forskolin, an adenylatecyclase activator, P formation was stimulated and the stimulationwas counteracted by the concomitant presence of prolactin, indicatingthat prolactin did not interfere with the LH-HCG receptor. Incells from smaller follicles, or in cells from follicles aspiratedfrom the natural cycle prior to the endogenous LH peak, P formationwas stimulated by HCG but the addition of prolactin did notreduce this stimulatory effect. The results are discussed inrelation to earlier reports on prolactin effects in vitro bothon laboratory animals and human material.