Effects of gonadotropin‐releasing hormone on plasma sex hormones in rana esculenta. in vivo studies

Abstract

Effects of gonadotropin‐releasing hormone (GnRH) on plasma levels of sex hormones were studied in intact, hypophysectomized, and hypophysectomized plus gonadectomized males and females of Rana esculenta. Specimens were injected subcutaneously with 20 ng of GnRH, and sacrificed soon after the injection (time 0), and at two subsequent intervals of 5 and 24 h. Levels of plasma androgens (testosterone plus dihydrotestosterone) and estradiol‐17β were evaluated by radioimmunoassay. Hypophysectomy and hypophysectomy plus gonadectomy significantly decreased plasma androgens and estradiol‐17β levels. A significant increase of plasma androgens in hypophysectomized specimens was observed 5 h after injection, whereas no apparent effect was observed after 24 h. GnRH also increased estradiol‐17β levels in intact and hypophysectomized specimens. It was suggested that GnRH affects sex steroid hormones release by acting directly on the gonads.

Key words:

• Amphibians
• Androgens
• Estradiol‐17β
• GnRH