AN UPWARD SHIFT OF INTRACELLULAR PH RATHER THAN THE FINAL ABSOLUTE PH VALUE IS CRITICAL FOR CONTROLLING GAP JUNCTION PERMEABILITY IN TUMOR PROMOTER-TREATED CELLS

The tumor promoter TPA is found to inhibit gap junction permeability in monolayer cultures of hamster fibroblasts. This effect is associated with an increase in intracellular pH. Here we show that neither an increase in pH(i) alone nor TPA treatment under conditions preventing pH(i)-shift affect gap junction permeability. It is not the level of pH(i) reached, but rather the pH(i)-shift itself that is essential for the inhibition of gap junction permeability in the presence of TPA.