Intracellular microinjection of alkaline buffers reversibly inhibits the initial phase of hormone action in meiosis reinitiation of starfish oocytes.
Intracellular microinjection of alkaline Hepes-KOH buffers, which increases intracellular pH (pHI) from 6.92 to 7.70 in fully grown prophase-blocked oocytes of the starfish Marthasterias glacialis, like external application of ammonia and other weak bases (M. Doree, K. Sano, and H. Kanatani, 1982, Dev. Biol. 90, 13-17), inhibited meiosis reinitiation induced by 1-methyladenine (1-MeAde) or dithiothreitol (DTT), a mimetic of the hormone. Oocytes could be released from inhibition by raising the concentration of hormone or of its mimetic. Increasing pHI to 7.70 neither inhibited nor delayed meiosis reinitiation when pH was clamped after the end of the hormone-dependent period, the period during which 1-MeAde is required in the external medium for meiosis to occur, whereas it blocked the action of the hormone at low concentration when performed before the end of the hormone-dependent period. When hormone concentration was higher, germinal vesicle breakdown (GVBD) occurred, but duration of the hormone-dependent period was increased. Delay introduced by alkalinization for oocytes to reach GVBD after 1-MeAde addition was smaller at high than at medium concentrations of the hormone. Increasing pHI did not inhibit action of MPF, the cytoplasmic maturation factor which induces GVBD and the subsequent process of meiotic maturation following hormonal treatment of prophase-blocked oocytes.
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006531:HEPES / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects*; D008845:Microinjections; D009865:Oocytes / Q000166:cytology*; D010063:Ovum / Q000166:cytology*; D011188:Potassium / Q000494:pharmacology; D017680:Potassium Compounds; D013215:Starfish
D006878:Hydroxides; D017680:Potassium Compounds; C008407:1-methyladenine; D000225:Adenine; D011188:Potassium; D006531:HEPES; D004229:Dithiothreitol; C029943:potassium hydroxide