title: Stimulatory effect of calcium ions on p-aminohippurate accumulation by rat kidney cortical slices.
abstract: The effect of external Ca2+ on p-aminohippurate (PAH) transport was examined using rat kidney cortical slices. External Ca2+ increased the initial rate of PAH uptake, markedly enhanced its maximal accumulation at steady-state conditions and depressed the efflux. Kinetic studies revealed that increasing external Ca2+ from 0 to 2.5 mM resulted in an increase in the Vmax of transport, while the apparent Km values remained constant. When the intracellular Na+ levels of the slices were equal, PAH accumulation was increased in the presence of Ca2+. A divalent cation such as Ba2+, Mn2+ or Sr2+ enhanced PAH accumulation to at least the same degree as Ca2+. While Mg2+ had no effect, La3+ exhibited a little stimulatory effect on the PAH accumulation. We suggest that the stimulatory action of Ca2+ on PAH accumulation is in part dissociated from that of Na+ gradient and that Ca2+ can be substituted by Ba2+, Mn2+ and Sr2+ with regard to the stimulation of PAH accumulation.
mesh_terms: D000618:Aminohippuric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D010130:p-Aminohippuric Acid / Q000378:metabolism*
chemical_list: D000618:Aminohippuric Acids; D002413:Cations, Divalent; D010042:Ouabain; D012964:Sodium; D002118:Calcium; D010130:p-Aminohippuric Acid