Abstract
The cortical collecting duct (CCD) mediates net secretion or reabsorption of protons according to systemic acid/base status. Using indirect immunofluorescence, we examined the localization and abundance of the vacuolar H(+)-ATPase and the AE1 anion exchanger in intercalated cells (IC) of rat kidney connecting segment (CNT) and CCD during acute (6 hr) metabolic (NH4Cl) acidosis and respiratory (NaHCO3) alkalosis. AE1 immunostaining intensity quantified by confocal microscopy was elevated in metabolic acidosis and substantially reduced in metabolic alkalosis. AE1 immunostaining was restricted to Type A IC in all conditions, and the fraction of AE1+IC was unchanged in CNT and CCd. Metabolic acidosis was accompanied by redistribution of H(+)-ATPase immunostaining towards the apical surface of IC, and metabolic alkalosis was accompanied by H(+)-ATPase redistribution towards the basal surface of IC. Therefore, acute metabolic acidosis produced changes consistent with increased activity of Type A IC and decreased activity of Type B IC, whereas acute metabolic alkalosis produced changes corresponding to increased activity of Type B IC and decreased activity of Type A IC. These data demonstrate that acute systemic acidosis and alkalosis modulate the cellular distribution of two key transporters involved in proton secretion in the distal nephron.
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