Redistribution of Na+/H+ exchanger isoform NHE3 in proximal tubules induced by acute and chronic hypertension

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Abstract
Redistribution of apical Na+/H+exchangers (NHE) in the proximal tubules as a plausible mechanism of pressure natriuresis was investigated with confocal immunofluorescence microscopy in Sprague-Dawley rats (SD), spontaneously hypertensive rats (SHR), and two-kidney, one-clip Goldblatt hypertensive rats (GH). NHE isoform NHE3 was localized in the brush border of proximal tubules in SD. Twenty minutes of induced acute hypertension (20–40 mmHg) resulted in a pronounced redistribution of isoform NHE3 from the brush border into the base of microvilli, where clathrin-coated pits were localized. Prehypertensive young SHR (5 wk old, mean blood pressure 105 ± 3 mmHg, n = 11) produced similar findings. However, NHE3 was found to concentrate in the base of microvilli in adult SHR (12 wk old, mean blood pressure 134 ± 6 mmHg, n = 12) and nonclipped kidneys of GH (mean blood pressure 131 ± 6 mmHg, n = 6). In clipped kidneys of GH, which were not exposed to the hypertension because of the arterial clips, NHE3 was localized on the brush border as in normal SD. No further redistribution of NHE3 was detected in adult SHR or GH when acute hypertension was induced. Since both acute and chronic increase of arterial pressure can provoke the redistribution of apical NHE in proximal tubules, the pressure-induced NHE redistribution could be a physiological response and an integral part of pressure natriuresis.