Basolateral membrane Na+/H+ antiport, Na+/base cotransport, and Na+-independent Cl-/base exchange in the rabbit S3 proximal tubule.
The basolateral membrane Na+ and Cl(-)-dependent acid-base transport processes were studied in the isolated perfused rabbit S3 proximal straight tubule. Intracellular pH (pHi) was measured with 2'7'-biscarboxyethyl-5,6-carboxyfluorescein (BCECF) and a microfluorometer coupled to the tubule perfusion apparatus. Reduction of basolateral HCO3- from 25 to 5 mM caused pHi to decrease at a rate of 0.81 pH/min. Approximately 50% of this rate was Na+-dependent, 30% Cl(-)-dependent and 20% Na+ and Cl(-)-independent. Two basolateral Na+-dependent acid base transport pathways were detected: (a) an amiloride-sensitive Na+/H+ antiporter and (b) a stilbene-sensitive Na+/base cotransporter. No evidence was found for a Na+-dependent Cl-/base exchanger. The Cl(-)-dependent component of basolateral base efflux was mediated by a stilbene-sensitive Na+-independent Cl-/base exchange pathway. The results suggest that the acid base transport pathways of the basolateral membrane of the S3 proximal tubule differ from more proximal nephron segments.
Kurtz
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I
Department of Medicine, University of California, Los Angeles School of Medicine 90024.
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001485:Basement Membrane / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D011817:Rabbits; D049992:Sodium Chloride Symporters; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters
D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D005452:Fluoresceins; D049992:Sodium Chloride Symporters; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein