Publication Abstract

Changes in plasma gonadotrophin and sex-steroid hormones, and in sperm production of Striped Bass after treatment with controlled-release GnRHa - delivery systems

Changes in plasma gonadotrophin andsex-steroid hormones, and in sperm production of Striped Bass after treatment withcontrolled-release GnRHa - delivery systems

C.C. Mylonas, A.P. Scott, E.L.M. Vermeirssen and Y. Zohar

Spermiating striped bass (Morone saxatilis), a perciform fish, were treated withtwo controlled- release gonadotrophin-releasing hormone agonist (GnRHa)- delivery systems,and the resulting changes in plasma gonadotropin II (GTH II), testosterone (T),11-ketotestosterone (11-KT), 17,20 beta -dihydroxy-4-pregnen-3-one (17,20 beta -P), and17,20 beta ,21-trihydroxy-4-pregnen-3-one (17,20 beta ,21-P) were correlated with changesin milt production and sperm density. GnRHa-delivery systems induced a sustainedelevation of plasma GnRHa and GTH II for 14 days. Plasma T levels were unchanged afterGnRHa treatment, while 11-KT levels increased significantly. Plasma 17,20 beta -P alsoincreased after GnRHa treatment and remained elevated compared to levels in controls,while plasma 17,20 beta ,21-P levels were unaffected. Both GnRHa-delivery systems inducedmany-fold increases in total expressible milt, lasting throughout the 14 days of thestudy. Sperm density decreased 2 days after GnRHa treatment, with a subsequent increase byDay 7. This study demonstrates that GnRHa-delivery systems induce a sustained elevation ofplasma GTH II levels in striped bass, resulting in a long-term enhancement of miltproduction. The endocrine changes observed suggest that 11-KT and 17,20 beta -P, but not17,20 beta ,21-P, are mediating the effects of GTH II on spermiation.

Reference:

C.C. Mylonas, A.P. Scott, E.L.M. Vermeirssen and Y. Zohar  (1997) Changes in plasma gonadotrophin andsex-steroid hormones, and in sperm production of Striped Bass after treatment withcontrolled-release GnRHa - delivery systems, Biology of Reproduction, 57: 669-675

C.C. Mylonas, A.P. Scott*, E.L.M. Vermeirssen* and Y. Zohar

Biology of Reproduction, 57: 669-675