Trans-stimulation effect on H(+)-organic cation antiport system in rat renal brush-border membranes.
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.
Katsura
T
T
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Japan.
Maegawa
H
H
Tomita
Y
Y
Takano
M
M
Inui
K
K
Hori
R
R
D000818:Animals; D001692:Biological Transport; D002250:Carbon Radioisotopes; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000378:metabolism
D002250:Carbon Radioisotopes; D013757:Tetraethylammonium Compounds; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D019789:Tetraethylammonium