Differential permeability of murine visceral yolk sac to thymidine and to hydroxyurea☆

[摘要] Mouseembryosatthe10–12-somitestageofdevelopmentwereexcisedfromtheuteruseitherwithorwithouttheencapsulatingvisceralyolksacandwereincubatedinvitroin3×10−7Mthymidine(methyl-T,5μCi/ml)for30minorin4×10−3Mhydroxyureafor45minwith[3H]thymidinepresentforthelast30min.Radioautogramsofnucleiofneuralepitheliumenabledanestimateoftheeffectivenessofthebarrierimposedbythevisceralyolksacmembranetothepassageofthymidineandhydroxyurea.Labelingofnucleiintheneuralepitheliumshowedthatthevisceralyolksaccauseda44%decreaseinfrequencyanda51%decreaseinintensityoflabel.Hydroxyureainhibitedlabelingby15%infrequencyand37%inintensityirrespectiveofthepresenceorabsenceofvisceralyolksac.Theseresultsshowthathydroxyureaandthepresenceofvisceralyolksacindependentlyinterferedwithlabelingoftheneuralepitheliumbythymidineandthatvisceralyolksaccausedaproportionallygreaterretardationoflabelthandidhydroxyurea.Nucleioftheendodermalepitheliumoftheinterveningyolksac,followingexposuretohydroxyurea,showedalabelingdecreaseof44%infrequencyand77%inintensity.Theinhibitoryeffectofhydroxyureaonyolksaclabeling,however,didnotalteryolksacpermeabilitytohydroxyurea.Theresultsindicatethatthevisceralyolksac,byofferingnodetectablebarriertohydroxyurea,permitspromptteratogenicactionofhydroxyureadirectlyupontheembryoandsuggestthatthevisceralyolksacisalikelycandidatetoaccountforreportsthatthe8.5-daymouseembryoinsitufailstolabelwithradioisotopicthymidine.

[学科分类] 生物科学（综合）