Proton gradient independent organic cation transport by HeLa cells

Transport by HeLa cells of the organic cation guanidine by a carrier-mediated mechanism that is inhibited by Na+, K+ and Li+, and in a dose-dependent manner by choline, cimetidine and tetraethylammonium was demonstrated recently. To characterize this transport process further, the influence of selected additional organic cations, inorganic cations and medium pH on guanidine transport by monolayer cultures of HeLa cells was investigated. It was observed to be inhibited by the antiviral drug amantadine and by dimethylamiloride. Significant inhibition of guanidine uptake was obtained with relatively high concentrations of the chloride salts of several inorganic cations including Mg++. Cytoplasmic acidification activating Na+-H+ exchanger-mediated Na+ uptake did not stimulate guanidine uptake and its efflux was the same over a 10-min rinse period, whether the pH of the rinse medium was 6.8 or 7.7.