ROLE OF NITRIC-OXIDE IN GONADOTROPIN-RELEASING HORMONE-DEPENDENT PROSTAGLANDIN-F2-ALPHA SYNTHESIS BY FROG (RANA-ESCULENTA) INTERRENAL GLANDDURING POST-REPRODUCTION

The aim of this study was to clarify the possible involvement of nitri c oxide (NO) on prostaglandin (PG) E-2-9-ketoreductase activity in the gonadotropin-releasing hormone (GnRH)-dependent PGF(2 alpha) synthesi s by the interrenal gland of the female water frog, Rana esculenta, du ring the post-reproduction. Interrenal glands were incubated in vitro with GnRH, NO donor (sodium nitroprusside, SNP), and inhibitors of pho spholipase C (compound 48/80), inositol triphosphate (decavanadate), c almodulin (calmidazolium), NO synthase (L-NAME), and PGE(2)-9-ketoredu ctase (palmitic acid). Production of PGE(2) and PGF(2 alpha) and NO sy nthase and PGE(2)-9-ketoreductase activities were determined. GnRH and SNP increased PGF(2 alpha) production and PGE(2)-9-ketoreductase acti vity, and decreased production of PGE(2) and GnRH increased NO synthas e activity. GnRH effects were blocked by all inhibitors, except for pa lmitic acid, which did not affect NO synthase activity, which is incre ased by GnRH. This study indicates that NO may be involved in regulati on of the R. esculenta post-reproduction through stimulation of PGE(2) -9-ketoreductase activity in GnRH-dependent PGF(2 alpha) synthesis by the frog interrenal gland.