Prolactin desensitizes the prostaglandin e1-dependent adenylyl cyclase in the rat prostate gland

Prior exposure of the rat ventral prostate to a high dose of ovine prolactin in vivo or in vitro caused the specific desensitization of the prostaglandin E₁-dependent adenylyl cyclase. Maximal desensitization was achieved in vivo 6 h after exposure to 100 μg prolactin and complete resensitization occurred after 7 days. No heterologous desensitization of the response of the cyclase to other hormones tested was observed. Incubation of isolated secretory cells with prolactin and prostaglandin E₁ desensitized the subsequent response to the same prostaglandin. Simultaneous exposure of the cells to indomethacin prevented the prolactin-induced effect. Prolactin could also induce similar changes in the prostaglandin E₁-dependent cyclase of rat Leydig cell tumour cells in vivo, suggesting that this may represent a phenomenon shared by other prolacting target organs. This study supports the hypothesis that prostaglandins may constitute second messengers for prolactin effects on the prostate gland.