AJP - Renal Physiology, Vol 261, Issue 5 774-F778, Copyright © 1991 by American Physiological Society

ARTICLES

Trans-stimulation effect on H(+)-organic cation antiport system in rat renal brush-border membranes

T. Katsura, H. Maegawa, Y. Tomita, M. Takano, K. Inui and R. Hori
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Japan.

Trans-stimulation effect on tetraethylammonium (an organic cation) transport was examined in rat renal brush-border membrane vesicles. The uptake of [14C]tetraethylammonium at pH 6.0-8.5 was stimulated by preloading the membrane vesicles with unlabeled tetraethylammonium. When the uptake was measured in preloaded membrane vesicles in the presence of carbonyl cyanide p-trifluoromethoxyphenylhydrazone, stimulation was observed at high pH but not at low pH. These results suggest that the mechanisms of the trans-stimulation effect on organic cation transport are different depending on the pH. When pH is low, the trans-stimulation is due to generation of an outward H+ gradient, which in turn stimulates [14C]tetraethylammonium uptake by H(+)-[14C]tetraethylammonium exchange. In contrast, when pH is high, the stimulation is due to direct exchange of tetraethylammonium for [14C]tetraethylammonium.

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