CHOLESTEROL MODULATES ORGANIC CATION-TRANSPORT ACTIVITY AND LIPID FLUIDITY IN RAT RENAL BRUSH-BORDER MEMBRANES

The role of cholesterol in organic cation transport was studied in rat renal brush-border membranes. H+ gradient-dependent uptake of the org anic cation tetraethylammonium in brush-border membrane vesicles was s timulated by cholesterol enrichment in a dose-dependent manner. The di ssipation rate of the H+ gradient, a driving force for organic cation transport in brush-border membranes, was reduced by cholesterol enrich ment. Tetraethylammonium uptake in the absence of H+ gradient was also stimulated by cholesterol enrichment, These findings indicate that ch olesterol modulates tetraethylammonium uptake by affecting the intrins ic activity of the organic cation transporter and the H+ gradient diss ipation rate, Therefore, cholesterol content should be an important de terminant for organic cation transport in renal brush-border membranes .