hCG-induced prostaglandin E2 and F2 alpha release in adult rat testis: role in Leydig cell desensitization to hCG.

Testicular levels of prostaglandin E₂ and F_2α were measured in decapsulated adult rat testis following hCG stimulation. Basal levels were, respectively, 342 ± 74 and 502 ± 89 pg/testis. Following hCG administration these basal values are not significantly modified up to 2 hours. From 2 to 24 hours the concentrations are clearly increased above the basal level: at 12 hrs they are 1925 ± 165 for E₂ and 3200 ± 190 for F_2α. Levels are back to normal at 48 hrs and remain so until 144 hrs. An identical pattern of prostaglandin release is observed in vitro in Leydig cell preparations isolated at different times following in vivo hCG injection. This suggests that prostaglandins are secreted by Leydig cells. In hypophysectomized animals the release of both prostaglandins E₂ and F_2α is similar to controls indicating that prostaglandin secretion is not directly linked to testosterone production. alternatively testosterone injections (10 mg) does not modify prostaglandin levels. Binding sites for prostaglandins E₁, E₂ and F_2α are present on the Leydig cells and consequently Leydig cell function may be modulated by endogenous or exogenous prostaglandins. Their level is slightly increased at 24 hrs following hCG stimulation. Since the acute changes in prostaglandin E₂ and F_2α secretion occur during the period of “desensitization” and of acute “down regulation” of the LH-hCG receptor in the Leydig cells it is suggested that prostaglandins are involved in both phenomena.