Effects of steroid hormones on in vitro oocyte maturation in white sturgeon (Acipenser transmontanus)

The in vitro effects of several steroids on the maturation of intact white sturgeon (Acipenser transmontanus) ovarian follicles were investigated. At the highest concentration (1024 ng ml(-1) for the C21 steroids and 1139 ng ml(-)1 for the C19 steroids), all of the C21 steroids tested, progesterone (P4), 17 alpha -hydroxyprogesterone (17OHP), 17 alpha ,20 beta -dihydroxy-4 -pregnen-3-one (17,20 beta -P), 17 alpha,(20 beta ,21-trihydroxy-4-pregnen- 3-one 20 beta -S), 11-deoxycortisol (S) and cortisol (F), as well as testos terone (T) induced germinal vesicle breakdown (GVBD) at 14 and 22 h. At 6 h , only P4 and 17,20 beta -P induced maturation at the highest concentration (1024 ng ml(-)1). At 14 and 22 h, 11-deoxycortisol was the most potent ste roid inducer of GVBD followed by P4, 17OHP, 17,20 beta -P, and 20 beta -S. The steroid 11 beta -hydroxytestosterone (11 beta OHT) was completely ineff ective at all concentrations and exposure times. The C21 steroids induced o ocyte maturation at concentrations ranging from 4 to 1024 ng ml(-1), wherea s T induced GVBD at 225 to 1139 ng ml(-1). Calculation of the mean effectiv e concentration that induced 50% GVBD (EC50) from the 22 h incubations reve aled the following order of potencies: S > P4 > 17OHP > 17,20 beta -P > 20 beta -S > > F > T. These bioassay results, together with previous findings on the endogenous production of steroids by ovarian follicles from gonadotr opin-primed females, indicate that more than one steroid has a biological r ole in the resumption of meiosis in sturgeon oocytes and provides empirical evidence for P4, 17OHP, S, 20 beta -S, and 17,20 beta -P as maturation-ind ucing steroids in white sturgeon.