GTH-II BUT NOT GTH-I INDUCES FINAL MATURATION AND THE DEVELOPMENT OF MATURATIONAL COMPETENCE OF OOCYTES OF RED SEABREAM IN-VITRO

The effects of red seabream gonadotropins (PmGTH I and PmGTH II) on th e induction in vitro of germinal vesicle breakdown (GVBD) and the deve lopment of maturational competence (responsiveness to maturation-induc ing steroid) were examined in the oocytes of red seabream. PmGTH II wa s highly effective in inducing GVBD in both maturationally incompetent (45.6 +/- 3.2% GVBD at a concentration of 300 ng/ml) and competent oo cytes (42.3 +/- 0.4% GVBD at a concentration of 300 ng/ml). 17,20 Chi- Dihydroxy-4-pregnen-3-one (DHP, 10 ng/ml) increased the frequency of G VBD induced by PmGTH II. PmGTH I (33, 100, 300, and 900 ng/ml) a as un able to induce GVBD at any tested concentration in the presence or abs ence of DHP. Actinomycin D (1 mu g/ml) and cycloheximide (1 mu g/ml) t otally inhibited the PmGTH II-induced GVBD in the presence and in the absence of DHP! Both PmGTH I and PmGTH II stimulated in vitro producti on of 11-ketotestosterone in sliced testes of red seabream in a simila r potency. These results indicate that PmGTH II, but not PmGTH I, indu ces the final maturation of oocytes, as well as the development of the maturational competence of oocytes, in red seabream. (C) 1998 Academi c Press.