Endocrine Abstracts

PGE₂ stimulates progesterone synthesis in the primate corpus luteum, apparently via cAMP. Human GL cells express functional EP1 and EP2 receptors via which PGE₂ elevates the intracellular calcium and cAMP concentrations respectively (Harris et al, 2001, BBRC 285:1089). In the present study, we have determined the involvement of EP1 and EP2 receptors in the stimulation of cAMP accumulation and progesterone synthesis in these human ovarian cells. Human GL cells (recovered from the follicular aspirates of women undergoing controlled hyperstimulation for assisted conception with informed patient consent and approval of the Local Ethics Committee) were isolated on 60% Percoll and cultured in vitro at 37 deg C at a density of 50,000 cells/ml in serum-supplemented medium. On day 3 of culture, cells were treated with 0-3microM PGE₂ ± 10microM SC19220 or 10microM AH6809 (preferential antagonists of EP1 and EP2 receptors respectively) for 24h. Cyclic AMP and progesterone concentrations, measured by RIAs, were each stimulated in a concentration-dependent manner by PGE₂. At the maximum tested concentration of 3microM, PGE₂ increased cAMP accumulation by 19.5 ± 9.4-fold (mean plus/minus SE; n=3; P<0.01), 27.9 plus/minus 15.0-fold (P<0.05) and 5.3 plus/minus 1.7-fold (P<0.01) in the absence of antagonists, with SC19220 and with AH6809, respectively. In the same cells, 3microM PGE₂ stimulated progesterone production by 78.2 plus/minus 10.6% (P<0.01) and 47.3 plus/minus 8.7% (P<0.05) in the absence of receptor antagonists and in the presence of SC19220, respectively, but had no significant effect in cells co-treated with AH6809. We conclude that both EP1 and EP2 receptors participate in the steroidogenic response of human GL cells to PGE₂ and that the ability of PGE₂ to stimulate progesterone synthesis is not reliant solely on the elevation of intracellular cAMP accumulation. (Supported, in part, by Wellcome Trust Project Grant 056630)