Abstract

The potency of various estrogens, androgens and progestogens at different concentrations and incubation periods on inducing final oocyte maturation in vitrowas investigated. At the highest concentration (1000 ng/ml), all of the C₂₁ steroids tested, progesterone (P₄), 17α-hydroxyprogesteron (17-OHP), 17α,20ß-dihydroxy-4-pregnen-3-one (17, 20ßP), as well as C₁₉ steroids, testosterone (T) and androsteindione (AD) were able to induce germinal vesicle breakdown (GVBD), whereas C₁₈ steroids, estrogens (E₁ and E₂) were found totally ineffective in inducing oocyte maturation at all the concentrations and exposure time. The relative potency of steroids were progestogens > androgens > estrogens. Among the steroids tested, 17,20βP appeared as the most potent oocyte maturation inducing steroid, causing 46% GVBD at the lower concentration of 10 ng/ml at 72 h exposure. The next most potent steroid was 17-OHP, inducing 25% GVBD at 72 h.  The relative response among progestogens were 17, 20βP > 17-OHP > P₄. These data suggest that 17,20βP is the major maturation-inducing steroid (MIS) in Barilius vagra and both the duration of exposure and the hormonal concentration had a positive influence on the percentage of germinal vesicle breakdown.

Key words: In vitro, oocyte maturation, germinal vesicle breakdown, estrogens, androgens, progestogens.