AJP - Renal Physiology, Vol 249, Issue 3 417-F423, Copyright © 1985 by American Physiological Society
Intracellular pH in the isolated perfused rabbit proximal straight tubule
S. Sasaki, T. Shigai and J. Takeuchi
For the purpose of measuring the intracellular pH (pHi) of the mammalian
renal proximal tubule, a liquid membrane pH microelectrode was made using a
neutral hydrogen ion-selective carrier. The pHi of the rabbit proximal
straight tubule perfused in vitro with a solution containing 25 mM HCO3-
was 7.22 +/- 0.03. We noted a value significantly lower than the bath pH of
7.44 +/- 0.02 but significantly higher than the pHi of 6.62 +/- 0.03
predicted for passive H+ distribution. Replacement of luminal Na+ with
choline quickly (within 1 min) decreased pHi from 7.25 +/- 0.05 to 7.10 +/-
0.05 (P less than 0.001). This change was reversible when Na+ was added
again in the luminal solution. A reduction of luminal Na+ from 20 mM to 0
also reduced pHi from 7.15 +/- 0.06 to 7.04 +/- 0.08, and this pHi
reduction was blocked by luminal addition of 1 mM amiloride. However, pHi
reduction induced by luminal Na+ removal was not affected by luminal
addition of 1 mM SITS. Replacement of bath Na+ with choline also reversibly
reduced pHi from 7.27 +/- 0.02 to 7.15 +/- 0.02 (P less than 0.001), but
this change was totally blocked by the presence of 1 mM SITS. Accordingly,
these data suggest that a Na+-H+ exchanger exists in the luminal membrane
of the intact rabbit proximal straight tubule.
