Oocyte hydration in the Japanese eel (Anguilla japonica) during meiosis resumption and ovulation.

In this study, to elucidate the mechanisms of oocyte hydration in the Japanese eel (Anguilla japonica), we examined the in vivo and in vitro morphological changes and hydration process occurring during oocyte maturation and ovulation. We also investigated the effects of the presence of ovarian follicles, aquaporin water permeability (HgCl(2)), and yolk proteolysis (bafilomycin A1) inhibitors, gap junction uncouplers (carbenoxolone and 1-octanol), a 3beta-hydroxysteroid dehydrogenase inhibitor (trilostane), and a P450 antagonist (aminoglutethimide) on oocyte hydration during in vitro oocyte maturation and ovulation. The oocytes underwent more than threefold increase in volume during maturation and ovulation, which was artificially induced by injecting salmon pituitary extracts and 17,20beta-dihydroxy-4-pregnen-3-one (DHP).