Characteristics of tetraethylammonium transport in rabbit renal plasma-membrane vesicles.
Transport of [14C]tetraethylammonium (TEA), an organic cation, was studied in brush-border (BBMV) and basolateral (BLMV) membrane vesicles isolated from rabbit kidney cortex. In BBMV, the presence of an outwardly directed H+ gradient induced a marked stimulation of TEA uptake against its concentration gradient (overshoot phenomenon), whereas a valinomycin-induced inside-negative potential had no effect on TEA uptake. In BLMV, TEA uptake was significantly stimulated by the presence of an outwardly directed H+ gradient and by an inside-negative potential, but the effect of H+ gradient was absent when the vesicles were chemically 'voltage clamped'. In BBMV, internal H+ stimulated TEA uptake in a non-competitive manner by binding at a site with apparent pKa of 6.87. External H+ inhibited TEA uptake through a direct interaction with the putative H+/organic-cation exchanger at a site with apparent pKa of 6.78. Changing external pH while maintaining the pH gradient constant produced a result similar to that obtained by changing external pH alone. Increasing external H+ showed a mixed-type inhibition of TEA uptake. These results suggest that in the rabbit TEA transport across the basolateral membranes is driven by an inside-negative potential and that transport across the brush-border membrane is driven by a H+ gradient via an electroneutral H+/TEA antiport system.
Jung
J S
JS
Department of Physiology, College of Medicine, Pusan National University, Korea.
Kim
Y K
YK
Lee
S H
SH
D000818:Animals; D017920:Antiporters; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000378:metabolism / Q000648:ultrastructure*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D011817:Rabbits; D013757:Tetraethylammonium Compounds / Q000493:pharmacokinetics*
D017920:Antiporters; D002352:Carrier Proteins; D008565:Membrane Proteins; D013757:Tetraethylammonium Compounds