title: Na+ gradient-dependent p-aminohippurate (PAH) transport in rat basolateral membrane vesicles.
abstract: The relationship between the transmembrane Na+ gradient and p-aminohippurate (PAH) transport was examined in isolated rat basolateral membrane vesicles. A 100 mM Na+ gradient (o leads to i) accelerated the influx of 50 microM [3H]PAH whereas similar gradients of choline+, K+, or Li+ did not. The sodium effect was not due to a diffusion potential. The Na+ gradient (o leads to i) decreased the apparent Michaelis constant for PAH from 0.167 +/- 0.016 to 0.054 +/- 0.016 mM and increased the maximum flux rate from 116.00 +/- 13.50 to 427.34 +/- 98.96 pmol/mg/min. An "overshoot" of [3H]PAH influx (159 +/- 4% of the equilibrium value) could be demonstrated only in the presence of a Na+ gradient (o leads to i) plus an opposing gradient of unlabeled PAH (i leads to o). These results suggest that PAH transport and the Na+ gradient are functionally related. A model for cellular uptake of PAH by a Na+ gradient-dependent anion exchange mechanism is presented.
mesh_terms: D000618:Aminohippuric Acids / Q000378:metabolism*; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors; D010130:p-Aminohippuric Acid / Q000378:metabolism*
chemical_list: D000618:Aminohippuric Acids; D007473:Ion Channels; D012964:Sodium; D010130:p-Aminohippuric Acid