AJP - Renal Physiology, Vol 245, Issue 4 462-F469, Copyright © 1983 by American Physiological Society
Absence of Cl- -OH- or Cl- -HCO3- exchange in the rabbit renal proximal tubule
G. J. Schwartz
Coupled entry of Na+ and Cl- into the cell may mediate salt and water
absorption by the renal proximal tubule. Other leaky epithelia have been
shown to have parallel luminal Na+-H+ and Cl- -OH- exchangers that can
serve in concert as a major pathway for NaCl absorption. Experiments were
designed to test whether Cl- -OH- or Cl- -HCO3- exchange occurs in the
isolated perfused rabbit proximal convoluted tubule and thereby whether
neutral transcellular NaCl absorption could be a possible mode of active
transport in this segment. The studies described here make use of a
lumen-to-cell gradient for Cl- to drive OH- from cell to lumen, causing an
increase in the rate of H+ disappearance from the luminal fluid.
Superficial proximal convoluted tubules were perfused in vitro with acidic
solutions (pH 6) that were generally free of organic solutes. The bathing
solution contained organics, colloid, and less than 10% of perfusate H+
concentration. H+ disappearance was calculated from the difference in pH
between perfused and collected fluid, flow rate, and buffer capacity of the
perfusate. The removal of Na+ from perfusate and bath reduced H+ efflux to
68% of control, a smaller effect than that noted previously in the presence
of organic solutes. When Na+-containing solutions were used, bilateral
replacement of Cl- by NO3-, isethionate, or SO2-(4) failed to reduce H+
efflux, but rather resulted in a 11% increase in H+ flux.(ABSTRACT
TRUNCATED AT 250 WORDS)
