Hydrogen ion cotransport by the renal brush border glutamate transporter

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Abstract
Na+-ion dependent glutamate transport into rabbit renal brush border membrane vesicles is stimulated by low external pH and inhibited by low internal pH. Imposition of a pH difference (.DELTA.pH) (interior alkaline) across the vesicle membrane drives glutamate accumulation in the absence of other driving forces. This process requires Na+ but is not due to generation of an Na+ gradient in response to .DELTA.pH. Internal K+ stimulates both the rate and extent of gutamate accumulation, although K+ is not absolutely required for transport. Internal H+ inhibits the rate of gutamate accumulation by decreasing this K+ stimulation. External K+ inhibits glutamate influx, and this inhibition can be overcome by lowering the external pH. Apparently, H+ is cotransported with glutamate and in the absence of internal K+, H+ can fulfill the requirement for a countertransported ion.