Further experimental evidence in support of the involvement of ovarian follicles in oocyte maturation of the Indian catfish, Mystus vittatus.

The role of the ovarian follicular layer in the oocyte maturation of the Indian catfish, Mystus vittatus, was investigated in vitro using cyanoketone and epostane (specific inhibitors of the 3 beta-hydroxysteroid dehydrogenase enzyme system). Folliculated oocytes incubated with luteinizing hormone (LH) at the concentration of 10 micrograms/ml induced 67.7 +/- 1.5% of germinal vesicle breakdown (GVBD). When the oocytes were incubated with LH + cyanoketone or epostane, there was a significant drop in the frequency of GVBD. It revealed that the maturational response of M. vittatus oocytes to LH depends on the synthesis of delta 4 steroids (probably 17 alpha,20 beta-dihydroxy-4-pregen-3-one; 17 alpha,20 beta-diOHprog) from the follicular layer since both the inhibitors failed to abolish the maturational effect of 17 alpha, 20 beta-diOHprog (the most potent maturation-inducing steroid for this species).