title: Glucose and alanine inhibition of phosphate transport in renal microvillus membrane vesicles.
abstract: Transport interactions among phosphate, glucose, and alanine were evaluated in brush border membrane vesicles isolated from the rabbit renal cortex. Both glucose and alanine inhibited the Na+ gradient-stimulated uphill accumulation of phosphate. Neither glucose nor alanine inhibited the phosphate uptake measured in the absence of Na+ or in the presence of a collapsed Na+ gradient shunted with amphotericin B. Phosphate and alanine inhibited the Na+ gradient-stimulated uphill accumulation of glucose but not the glucose uptake measured in the presence of a collapsed Na+ gradient shunted with amphotericin B. Alanine, which was more potent than glucose or phosphate in inhibiting Na+ gradient-stimulated solute transport, was also more potent than glucose or phosphate in stimulating the uptake of Na+ into the vesicles. We conclude that the inhibitory interactions among phosphate, glucose, and alanine probably represent indirect effects resulting from solute-induced alterations in the transmembrane electrochemical Na+ gradient rather than direct effects resulting from competition for a polyfunctional carrier or from allosteric interactions. Such a mechanism could explain the inhibitory interactions among phosphate, glucose, and alanine that have been observed in the intact proximal tubule.
mesh_terms: D000409:Alanine / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism*; D003864:Depression, Chemical; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
chemical_list: D010710:Phosphates; D012964:Sodium; D005947:Glucose; D000409:Alanine