TETRAETHYLAMMONIUM TRANSPORT IN RENAL BRUSH-BORDER MEMBRANE-VESICLES OF THE RABBIT

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  • 1 January 1987
    • journal article
    • research article
    • Vol. 240  (1) , 308-313
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 < .05: 0.250-0.425) mM; Vmax, 2.13 (CL for P < .05: 1.98-2.32) nmole/mg of protein .times. 15 sec]. Other organic cations interact with this exchange mechanism: mepiperhenidol 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.