Differential effects of external pH alteration on intracellular pH in rat coronary and cardiac myocytes

Changes in extracellular pH (pH_o) induce changes in the intracellular pH (pH_i) of cardiac myocytes that are slow and attenuated. Little however is known about the effects of changing pH_o on the pH_i of the coronary smooth muscle cells. We have therefore directly compared the effects of altering pH_o on pH_i of both coronary and cardiac myocytes. Carboxy-SNARF was used in single cells to measure pH_i. Alteration of pH_o caused corresponding changes in pH_i that were large (70–80 % of pH_o) and rapid in coronary myocytes compared to cardiac myocytes. In contrast, changes of pH_i produced by weak acids or bases produced similar pH_i responses in both types of cells. It is suggested that the differential effects of pH_o on coronary and cardiac cells may be functionally significant, as it will allow rapid alteration of coronary perfusion to meet tissue needs, while maintaining cardiac output.Supported by the BHF and MRC