Development of structure and function in the mammalian yolk sac: III. The development of amino acid transport by rabbit yolk sac☆

[摘要] Rabbityolksacsobtainedfromfetusesolderthan20days'gestationactivelyaccumulatedl-valine,l-isoleucine,l-phenylalanine,l-alanine,andl-methionine.Glycine,l-proline,betaine,l-lysine,α-methylglucoside,and6-deoxyglucosewerenotactivelyaccumulated.Theyolksacisapolarizedmembraneasitwascapableofeffectinganettransferofl-valineacrossitsfullthicknessfrommucosaltoserosalcompartmentsagainstaconcentrationgradient.l-Valinerapidlyequilibratedwithintracellularwaterintissueobtainedfromfetusesyoungerthan20days'gestation,butaccumulationagainstaconcentrationgradientdidnotoccur.Inhibitionofvalineuptakeinsuchtissuebyl-methionineandl-isoleucinesuggestedthatacarrier-mediatedprocesswasinvolved.Therateofexitofpreloadedl-valinefrom17-dayyolksacswassimilartothatfoundin28-to30-dayyolksacs.AstudyoftheeffectofvalineconcentrationontheinitialrateofuptakebythemorematureyolksacsindicatedsaturationkineticswithanapproximateKtof2.1mM.Nosaturationofthetransportrateby17-dayyolksacswasfoundupto10mMconcentrationofvaline.

[学科分类] 生物科学（综合）