Publication Abstract

Gonadotrophin-releasing hormone agonist stimulates milt fluidity and plasma concentrations of 17,20beta-dihydroxylated and 5beta-reduced, 3alpha-hydroxylated C21 steroids in male plaice (Pleuronectes platessa).

Gonadotrophin releasing-hormone agonist stimulates milt amounts and plasma concentrations of 17,20β-dihydroxylated-steroids in male plaice

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

Spermiating male plaice were caught in the North Sea and acclimatised to laboratory conditions. In two experiments, males were injected intramuscularly with either microspheres or pellets containing gonadotrophin releasing-hormone agonist (GnRHa; D-Ala⁶, Pro⁹-Nethylamide-luteinising hormone releasing-hormone). The fish were bled at 2 to 5 day intervals. Individual blood plasma samples were assayed for testosterone and sulphated 17,20β-dihydroxy (`17,20(β) steroids. Pooled plasma samples were also assayed for the presence of free and sulphated 17,20β-dihydroxy-4-pregnen-3-one, free 11-ketotestosterone and glucuronidated testosterone and 11-ketotestosterone. Plasma concentrations of all steroids were significantly elevated by GnRHa from 2 to 5 days onwards following treatment. The most marked changes occurred in the concentrations of the sulphated `17,20β' steroids, which comprised of approximately equal amounts of 50-pregnane-3α,17,20β triol 20-sulphate and 5β-pregnane-30,17,20β-triol 20-sulphate; rising from c. 1 to 30-80 ng/ml in the first, and from c. 8 to 80 ng/ml in the second experiment). In another experiment, milt production was assessed at 10, 15, and 25 days following GnRHa implantation. Milt volumes were significantly enhanced by the GnRHa treatment, mainly due to hydration of the sperm.

Reference:

E.L.M. Vermeirssen, A.P. Scott, C.C. Mylonas and Y. Zohar, (1998). Gonadotrophin releasing-hormone agonist stimulates milt amounts and plasma concentrations of 17,20b-dihydroxylated-steroids in male plaice. General and Comparative Endocrinology, 112, 163-177.

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

General and Comparative Endocrinology, 112, 163-177