Response of large oocytes of Xenopus laevis to progesterone in vitro in relation to oocyte size and time after previous HCG-induced ovulation☆

摘要

TheinjectionofXenopuslaevisfemaleswithhumanchorionicgonadotropin(HCG)leadstoovulation(andmaturation)ofoocyteswhosediametersare1.2mmorlarger.However,whenXenopusoocytesareremovedfromtheirfollicularinvestmentsbymanualdissectionandexposedtothesteroid,progesterone,invitro,theyexhibitmaturationdowntoabout0.90mmindiameterwiththemajoritylargerthan1.0mmshowingapositiveresponse.Withineachfemalethelargeroftheoocytesundergomaturationearlierthansmallerones.Theresponseofoocytesalsowasshowntodependonthelengthoftimesincefemaleswerelaststimulatedtoovulate.Similar-sizedoocytesfromrecentlyovulated(stimulated)femalesmaturedmuchfasterthanthoseofuntreated,unstimulatedfemales.Indeed,eventhesmalleroocytesfromstimulatedfemalesoftenmaturedbeforethelargestoocytesoffemaleswithoutpreviousHCGinjection.Theexperimentsdemonstratethatthephysiologicalstateofanoocytecannotbeaccuratelydeducedsolelyfromitssizenorresponsetogonadotropins;unresponsivenesspresumablybeingduetoinabilityoffollicularelementstorespondtothetrophichormonesortransferthestimulustotheoocyteviatheappropriatesteroid.