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

Changes in extracellular pH (pHo) induce changes in the intracellular pH (pHi) of cardiac myocytes that are slow and attenuated. Little however is known about the effects of changing pHo on the pHi of the coronary smooth muscle cells. We have therefore directly compared the effects of altering pHo on pHi of both coronary and cardiac myocytes. Carboxy-SNARF was used in single cells to measure pHi. Alteration of pHo caused corresponding changes in pHi that were large (70-80% of pHo) and rapid in coronary myocytes compared to cardiac myocytes. In contrast, changes of pHi produced by weak acids or bases produced similar pHi responses in both types of cells. It is suggested that the differential effects of pHo 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.