Characterization of the Na+/H+ Exchanger in the Luminal Membrane of the Distal Nephron

Characterization of the Na+/H+ Exchanger in the Luminal Membrane of the Distal Nephron In the rabbit as well as the rat, a Na+/H+ exchanger is expressed in the apical membrane of both the proximal and distal tubules of the renal cortex. Whereas the isoform derived from the proximal tubule has been extensively studied, little information is available concerning the distal luminal membrane isoform. To better characterize the latter isoform, we purified rabbit proximal and distal tubules, and examined the ethylpropylamiloride (EIPA)-sensitive 22Na uptake by the luminal membrane vesicles from the two segments. The presence of 100 μm EIPA in the membrane suspension decreased the 15 sec Na+ uptake to 75.70 ± 4.70% and 50.30 ± 2.23% of the control values in vesicles from proximal and distal tubules, respectively. The effect of EIPA on 35 mm Na+ uptake was concentration dependent, with a IC50 of 700 μm and 75 μm for the proximal and distal luminal membranes. Whereas the proximal tubule membrane isoform was insensitive to cimetidine and clonidine up to a concentration of 2 mm, the 35 mm Na+ uptake by the distal membrane was strongly inhibited by cimetidine (IC50 700 μm) and modestly inhibited by clonidine (IC50 1.6 mm). The Journal of Membrane Biology Springer Journals

Characterization of the Na+/H+ Exchanger in the Luminal Membrane of the Distal Nephron

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Copyright © Inc. by 1998 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
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