Profiles of plasma gonadotropin and 17β-estradiol in the common carp, Cyprinus carpio L., as related to spawning induced by hypophysation or LH-RH treatment

Abstract

Plasma gonadotropin (GTH) and 17 beta-estradiol (17 beta-E2) levels and oocyte stage have been studied in the common carp, Cypinus carpio L., after classical "hypophysation" (two intraperitoneal pituitary injections of 0.3 mg/kg and 2.7 mg/kg at a 12-hr interval) or LH-RH treatment (two intracardiac injections of 3 micrograms/kg at a 3-hr interval). After the first pituitary injection of LH-RH treatment, GTH increase was followed by a significant increase of 17 beta-E2 7 hrs after the injection. The higher GTH levels after the second pituitary injection did not increase that secretion. After classical "hypophysation", one-half of the females ovulated. There was no difference between spawning and non-spawning fishes in relation to hormonal parameters. LH-RH treatment only induced a shifting of the nucleus.