Electrical properties of the Drosophila egg membrane☆

[摘要] ElectricalpropertiesoftheeggmembraneofDrosophilamelanogasterwereexaminedusingintracellularmicroelectrodes.Unfertilizedeggsandfertilizedeggsfortheperioduptothesyncytialblastodermstagewereused.AmongNa,K,andCl,Kwasmostpermeanttothemembrane.TheKpermeability,however,didnotcompletelydeterminethemembranepotential.Therestingpotentialinstandardsolutionwas−63.5±8.0mV(mean±SD)inunfertilizedeggscollectedwithin2–3daysaftervirginfliesstartedtolayeggs.Therestingpotentialinfertilizedeggswas−27.0±8.4mVwithin20minaftereggdeposition,whileitwas−55.1±6.5mVatthesyncytialblastodermstage.ThesechangesatdifferentdevelopmentalstageswereassociatedwithchangesintheK-dependenceofthemembrane.ThelargeramplitudeoftherestingpotentialwassuggestedtobeduetoincreasedKpermeabilitybutnottodecreasednonspecificleakage.Thecurrent-voltagerelationwaslinearthroughoutthestagesexamined.Actionpotentials,suchasthoseineggsofotheranimals,werenotobserved.HighCamediasignificantlyincreasedtheamplitudeoftherestingpotentialassociatedwithincreaseinthemembraneresistance.AremarkablenonlinealityintheI–VrelationappearedinhighCamedia,whichcausedcontinuouslyincreasinghyperpolarizationduringsustainedinwardcurrent.Eggsoftemperature-sensitivemutants,shits1andparats1showedpropertiessimilartothoseinwild-typeeggswithtransienttemperaturechanges.

[学科分类] 生物科学（综合）