Effect of pH on the water and electrolyte content of rat diaphragm

Abstract

The effect of variations of external pH (pH 6.2–8.2) on the water and ionic composition of rat diaphragm was studied. Tissue water, Na + and Cl − were barely affected by increasing external pH whereas tissue K + increased linearly; the pH-dependent cellular uptake of K + was abolished by ouabain. Ouabain (1 m m) produced a cellular swelling at pH 8.2 whereas at lower saline pH the control of cell volume was not affected by the cardiac glycoside. In Ca 2+-free salines (3 m m EDTA present) a marked cellular swelling was observed only at pH 8.2; 1 m m ouabain induced a swelling at both pH 7.2 and 8.2. The cellular swelling produced by ouabain or absence of Ca 2+ was associated with a net uptake of Na + and Cl −. At pH 6.2 and 7.2, a regulation of cell volume was found also in the absence of Na + (Li or Tris salines). The characteristics of the ouabain-insensitive (and Na +-independent) mechanism of volume control in diaphragm cells, i.e., dependence on pH and Ca 2+, are identical with those reported for renal tubular cells.