Basolateral membrane Na+/H+ antiport, Na+/base cotransport, and Na+-independent Cl-/base exchange in the rabbit S3 proximal tubule.
AUTOR(ES)
Kurtz, I
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=303722Documentos Relacionados
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