Effect of acidosis on glutamine transport by isolated rat renal brush-border and basolateral-membrane vesicles

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Abstract
Glutamine uptake was examined in isolated renal brush-border and basolateral membrane vesicles from control and acidotic rats. In brush border vesicles from acidotic animals, there was a significant increase in the initial rate of glutamine uptake compared with that in controls. Lowering the pH of the medium increased the initial rate of glutamine uptake in brush-border vesicles from acidotic, but not from control, rats. In brush-border vesicles from both groups of animals, 2 saturable transport systems mediated glutamine uptake. There was a 2-fold increase in the Vmax, of the low-affinity high-capacity system in the brush-border vesicles from the acidotic animals compared with that from control animals, with no alteration in the other kinetic parameters. There was no difference in glutamine uptake by the 2 saturable transport systems in basolateral vesicles from control and acidotic animals. Lowering the incubation medium pH increased the uptake of glutamine by basolateral vesicles from both control and acidotic rats to a similar extent. Apparently, during acidosis there are alterations in glutamine transport by both the basolateral and brush-border membrane which could enhance its uptake by the renal tubule cell for use in ammoniagenesis.