<i>In vitro</i> maturation and ovulation of oocytes of the catfish, <i>Heteropneustes fossilis</i> (Bloch): Effects of mammalian hypophyseal hormones, catfish pituitary homogenate, steroid precursors and metabolites, and gonadal and adrenocortical steroids

Abstract

Abstract Wolf and Quimby medium and its modified chemically‐defined version were found to be most suitable among the eight media tested for shortterm culture of oocytes of the catfish, Heteropneustes fossilis . The modified Wolf and Quimby was employed to evaluate the relative effectiveness of several hypophyseal and steroid hormones, as well as steroid precursors and metabolites in inducing in vitro maturation and ovulation in the catfish oocytes. With the exception of ovine luteinizing hormone (LH) which gave only a marginal response even at high dose levels, other mammalian hypophvseal hormones (FSH, TSH, LtH, STH and ACTH) and catfish pituitary homogenate were incapable of inducing oocyte maturation. Of the steroid precursors tested, pregnenolone, progesterone and their 17 α‐hydroxy derivatives were slightly effective in inducing oocyte maturation at high concentrations. Steroid metabolites (pregnanediol‐20 β) were ineffective. The sex steroids (testosterone, estrone, estriol and estradiol) did not induce oocyte maturation, while dehydroepiandrosterone and androstenedione gave only a nominal response even at high doses. Corticosteroids, principally hydrocortisone (F) and desoxycorticosterone (DOC) as also their acetates, were the most potent maturation‐inducing agents even at low concentrations. These results strongly suggest that inasmuch as LH and catfish pituitary homogenate per se do not induce oocyte maturation in vitro , the terminal hormones which act directly on the oocytes to induce maturation and ovulation are the corticosteroids principally, DOC and F. The significance of these findings in the hormonal control of ovulation in the catfish is discussed.