EFFECTS OF INCUBATION MEDIA ON MATURATION OF ISOLATED OVARIAN FOLLICLES OF SIBERIAN STURGEON (ACIPENSER BAERI BRANDT) INDUCED BY STURGEON GONADOTROPIC PREPARATION OR 17-ALPHA,20-BETA-DIHYDROXYPROGESTERONE

In vitro maturation of Siberian sturgeon follicles was studied followi ng induction with sturgeon gonadotropic preparations (aci-GTH, ED50) o r 17 alpha,20 beta-diOHP (ET50 and complete maturation (GVBD)). aci-GT H ED50 varied greatly, over an order of magnitude depending on female or incubation medium. Spontaneous maturation was recorded at different levels, for different females and in different media probably as a re sult of a peculiar situation between follicle state and medium. Analys is of variance demonstrated the great importance of the medium and its interaction with the follicle. The best preferred incubation medium i s based on Siberian sturgeon plasma characteristics because it provide s good discrimination of the female physiological state and it avoids ''abnormal'' responses. The optima for pH and osmotic pressure are app roximately pH 8 and 270-280 mosmol/l, respectively, although there wer e great individual variations of 17 alpha,20 beta-diOHP-dependent GVBD to pH and osmotic pressure. The 17 alpha,20 beta-diOHP ET50 is incuba tion medium-independent and readily discriminates the females. Some ot her observations are discussed in the light of the literature. (C) 199 7 Elsevier Science Inc.