The basic asymmetry of Na+-dependent glycine transport in Ehrlich cells.
Influx and efflux of glycine have been examined as a function of external and internal Na+ concentrations, respectively, when : formula: (see text) = O. With : formula: (see text) = O it was found that at comparable external and cellular Na+ levels, the Km for efflux was larger by an order of magnitude than the value for influx and the V for efflux was several times greater than the V for influx. For both fluxes the major effect of Na+ was to decrease the Km value. The observations are consistent with the conclusion that the Na+-dependent transport system is asymmetric per se. Influx and efflux of glycine were increased in a near linear manner by increasing the Na+ concentration from 13 to 100 mM, the half-time for glycine equilibration being a funcion of the Na+ concentration in absence of an electrochemical potential difference for Na+. In Na+-free media ([Na+] less than 5 mM) equilibration of glycine between cells and medium was not achieved after 60 min at 25 degrees C. With : formula: (see text) = O, efflux (or uptake) of glycine was not affected by internal (or external) K+ between 20 and 120 mM suggesting that K+ plays no direct role in Na+-dependent transport of glycine in Ehrlich cells.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002794:Choline / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D051379:Mice; D012964:Sodium / Q000494:pharmacology*
D008094:Lithium; D012964:Sodium; D002794:Choline; D005998:Glycine