title: Tetraethylammonium transport in renal brush border membrane vesicles of the rabbit.
abstract: The mechanisms involved in the transport of tetraethylammonium (TEA) in the rabbit renal brush border were investigated by using membrane vesicles. Transport of [14C]TEA (0.2 mM) was measured by a rapid filtration method. We have reported previously that an imposed pH gradient (pHi = 6, pHo = 7.4) stimulates the uptake of TEA markedly, yielding a transient overshoot of 200% above the equilibrium value. Here we demonstrate that an overshoot of similar magnitude can also be obtained in the presence of indirectly induced proton gradients, via the naturally occurring Na+/H+ exchanger or via the artificial K+/H+ exchanger nigericin. The TEA exchange mechanism is shown to be electroneutral, temperature-dependent and saturable [Km, 0.328 (CL for P less than .05: 0.250-0.425) mM; Vmax, 2.13 (CL for P less than .05: 1.98-2.32) nmole/mg of protein X 15 sec]. Other organic cations interact with this exchange mechanism: mepiperphenidol and morphine both cis-inhibited and trans-stimulated TEA uptake. Quinine, which was the most potent inhibitor of TEA uptake (57% inhibition at 10(-5) M), did not trans-stimulate. The mechanism appears to be specific for organic cations inasmuch as the organic anion p-aminohippurate did not cis-inhibit or trans-stimulate TEA uptake. These results demonstrate the presence of a H+/TEA exchange mechanism in the rabbit renal brush border membrane showing many similarities with that shown to be present in the rat.
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000648:ultrastructure*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism; D009020:Morphine / Q000494:pharmacology; D009550:Nigericin / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D027961:Potassium-Hydrogen Antiporters; D011803:Quinine / Q000494:pharmacology; D011817:Rabbits; D013696:Temperature; D013757:Tetraethylammonium Compounds / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D010880:Piperidines; D027961:Potassium-Hydrogen Antiporters; D013757:Tetraethylammonium Compounds; D009020:Morphine; C010482:mepiperphenidol; D011803:Quinine; D009550:Nigericin