TRANSPORT OF ORGANIC IONS IN RENAL CORTICAL LUMINAL AND ANTILUMINAL MEMBRANE-VESICLES

Abstract

Based upon saturability, kinetic analysis and specific inhibition, specific transport for the organic anion, p-aminohippurate was found in isolated luminal and antiluminal membrane vesicles from dog kidney cortex. The transport for organic anions in the 2 membranes differed from one another on the basis of kinetic parameters (Km, Vmax and Ki [inhibition constant] (for probenecid) and counterflow phenomenon (only the antiluminal membrane displayed the capacity to accelerate the exchange of p-aminohippurate). Also described is specific transport for the organic cation N1 methylnicotinamide in each membrane. The luminal and antiluminal transport of N1-methylnicotinamide are distinguished from one another by kinetic parameters (Km, Vmax and Ki for Darstine) and counterflow data (counterflow of N1-methylnicotinamide was observed only in the luminal membrane). The results are discussed in view of a proposed model to explain transepithelial transport of these organic ions.