Beta-endorphin inhibits prostaglandin synthesis in rat ovaries and blocks induced ovulation

• Published in: Prostaglandins 1995-02, Vol.49 (2), p.93-103
• Main Authors: Faletti, A., Viggiano, J.M., Gimeno, M.A.F.
• Format: Article
• Language: English
• Subjects: Animals; Arachidonic Acid - pharmacology; beta-Endorphin - pharmacology; Chorionic Gonadotropin - pharmacology; Dinoprost - biosynthesis; Female; Gonadotropins, Equine - pharmacology; Humans; In Vitro Techniques; Oocytes - drug effects; Ovary - drug effects; Ovary - metabolism; ovulation; Ovulation Induction; prostaglandins; Prostaglandins - biosynthesis; Prostaglandins E - agonists; Prostaglandins E - biosynthesis; Radioimmunoassay; Rats; Rats, Wistar; β-endorphin
• ISSN: 0090-6980
• DOI: 10.1016/0090-6980(94)00006-I

The aim of the present study was to explore the action of exogenous β-endorphin on the number of oocytes ovulated and on prostaglandin (PG) production in ovaries isolated from pregnant mare's serum gonadotropin/human chorionic gonadotropin(PMSGlhCG)-primed immature rats. An intrabursal injection of the opioid (0.084 μg) was given 4 hours after hCG and the number of oocytes within the oviducts on the following morning was reduced ( P < 0.05). The same effect was also attained with an intraperitoneal (IP) injection (0.5 μg). The time course of PG synthesis was quantified in ovaries of rats treated with an IP injection. Eight hours after hCG, prostaglandin content increased ( P < 0.01) and remained high until 12 hours after hCG ( P < 0.001). This increase was inhibited by the in vivo treatment with β-endorphin. On isolated ovaries, β-endorphin (10 −8 M) had a clear inhibitory action on prostaglandin production. β-Endorphin's effect on prostaglandin synthesis in the ovaries is of importance in the ovulatory process. The possible physiological role of β-endorphin merits further investigation.