In vivo and in vitro studies on the effects of mGnRH on oestradiol-17 beta inter-renal production in the female frog, Rana esculenta, during the post-reproductive period

Role of nitric oxide in gonadotropin-releasing hormone-dependent prostaglandin F2 alpha synthesis by frog (Rana esculenta) interrenal gland during post-reproduction

The aim of this study was to clarify the possible involvement of nitric oxide (NO) on prostaglandin (PG) E2-9-ketoreductase activity in the gonadotropin-releasing hormone (GnRH)-dependent PGF2 alpha synthesis by the interrenal gland of the female water frog, Rana esculenta, during the post-reproduction. Interrenal glands were incubated in vitro with GnRH, NO donor (sodium nitroprusside, SNP), and inhibitors of phospholipase C (compound 48/80), inositol triphosphate (decavanadate), calmodulin (calmidazolium), NO synthase (L-NAME), and PGE2-9-ketoreductase (palmitic acid). Production of PGE2 and PGF2 alpha and NO synthase and PGE2-9-ketoreductase activities were determined. GnRH and SNP increased PGF2 alpha production and PGE2-9-ketoreductase activity, and decreased production of PGE2 and GnRH increased NO synthase activity. GnRH effects were blocked by all inhibitors, except for palmitic acid, which did not affect NO synthase activity, which is increased by GnRH. This study indicates that NO may be involved in regulation of the R. esculenta post-reproduction through stimulation of PGE2-9-ketoreductase activity in GnRH-dependent PGF2 alpha synthesis by the frog interrenal gland.

A novel neuropeptide cellular mechanism in amphibian interrenal steroidogenesis

Interrenals of female Rana esculenta were incubated with gonadotropin-releasing hormone (GnRH), 9-ketoreductase inhibitor (palmitic acid), acetyl salicyclic acid, prostaglandin F2 alpha (PGF2 alpha), forskolin, isobutylmethyl xanthine (IBMX), dibutyril cyclic adenosine monophosphate (dbcAMP). Prostaglandin E2 (PGE2), PGF2 alpha, testosterone and 17 beta-estradiol were assessed on the incubation media. In addition, in the same interrenals, 9-ketoreductase and aromatase activities were evaluated. GnRH increased PGF2 alpha, 17 beta-estradiol, 9-ketoreductase and aromatase, and decreased PGE2 and testosterone. PGF2 alpha increased 17 beta-estradiol and aromatase, and decreased testosterone. Palmitic acid counteracted GnRH effects, while forskolin, IBMX and dbcAMP showed the same PGF2 alpha effects. These results suggest that GnRH stimulates 9-ketoreductase enhancing PGF2 alpha which in turn activates aromatase through cAMP mediation in the interrenal of Rana esculenta.