Inhibitory action of hypoxanthine on meiotic resumption of denuded pig follicular oocytes in vitro.
The present study was conducted to investigate the direct action of hypoxanthine, which has been reported to be present in pig follicular fluid, on spontaneous meiotic resumption of pig denuded oocytes in vitro. No oocytes, which were surrounded by a cumulus and some membrana granulosa cells directly adjacent to it from healthy antral follicles, underwent germinal vesicle breakdown (GVBD) when they were cultured in serum-supplemented 199 with or without 4 mM hypoxanthine. On the other hand, 81% of denuded oocytes prepared from such cumulus-oocyte-granulosa cell complexes showed GVBD after 24 h of culture. Hypoxanthine inhibited significantly this spontaneous resumption of meiosis in denuded oocytes. The inhibitory action of hypoxanthine was dose dependent at concentrations of 1-6 mM and was reversible following subsequent culture of the oocytes in hypoxanthine-free medium. However, premature chromosome condensation was observed in oocytes cultured in hypoxanthine-supplemented medium, and the oocytes released from the influence of hypoxanthine completed GVBD and reached the second metaphase slightly faster than those freshly isolated from the follicle. These results suggest that hypoxanthine inhibits spontaneous meiotic resumption of pig oocytes in vitro. However, the inhibitory action of hypoxanthine does not prevent all events involved in GVBD from occurring.
Miyano
T
T
Laboratory of Animal Breeding and Reproduction, Faculty of Agriculture, Kobe University, Japan.
Ebihara
M
M
Goto
Y
Y
Hirao
Y
Y
Nagai
T
T
Kato
S
S
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D015571:Follicular Fluid / Q000502:physiology; D006107:Granulosa Cells / Q000502:physiology; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008540:Meiosis / Q000187:drug effects; D008677:Metaphase; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D006080:Ovarian Follicle; D013552:Swine; D013997:Time Factors
D007042:Hypoxanthines; D019271:Hypoxanthine