title: Monovalent cation and ouabain effects on PAH uptake by rabbit kidney slices.
abstract: The effects of K+, Na+, and ouabain on para-aminohippurate (PAH) accumulation by rabbit kidney slices have been further examined. The present studies show that for maximum uptake of PAH to occur in Na+,K+-depleted slices extra-cellular Na+ and K+ ions are required together. Kinetic studies revealed that increasing the external K+ from 0 to 5 mM caused a decrease in the apparent Km of transport. The Vmax values were not changed significantly. In the presence of 5 mM K+, increasing Na+ concentration in the bathing medium from 0 to 145 mM produced an increase in the V max while the apparent Km remained constant. In the presence of 5 mM external K+, ouabain inhibition of PAH uptake was progressively and entirely antagonized by decreasing external Na+. Studies on kidney slices treated with ouabain in a Na+,K+-free medium in order to inhibit active electrolyte transport showed that PAH uptake under anaerobic conditions was specifically enhanced by Na+. This stimulation occurred when cell [Na+] was less than medium [Na+]. This Na+-dependent and energy-independent accumulation of PAH was inhibited by hippuric acid but not by N-methylnicotinamide.
mesh_terms: D000332:Aerobiosis; D000618:Aminohippuric Acids / Q000378:metabolism*; D000693:Anaerobiosis; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002414:Cations, Monovalent; D006626:Hippurates / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D011191:Potassium Deficiency; D011817:Rabbits; D012964:Sodium / Q000172:deficiency / Q000378:metabolism / Q000494:pharmacology*; D013268:Stimulation, Chemical; D010130:p-Aminohippuric Acid / Q000378:metabolism*
chemical_list: D000618:Aminohippuric Acids; D002414:Cations, Monovalent; D006626:Hippurates; D009536:Niacinamide; D010042:Ouabain; D012964:Sodium; D011188:Potassium; D010130:p-Aminohippuric Acid