DIFFERENTIAL-EFFECTS OF EXTERNAL PH ALTERATION ON INTRACELLULAR PH INRAT CORONARY AND CARDIAC MYOCYTES

Changes in extracellular pH (pH(o)) induce changes in the intracellula r 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 t he coronary smooth muscle cells. We have therefore directly compared t he effects of altering pH(o) on pH(i) of both coronary and cardiac myo cytes. Carboxy-SNARF was used in single cells to measure pH(i). Altera tion of pH(o) caused corresponding changes in pH(i) that were large (7 0 - 80% of pH(o)) and rapid in coronary myocytes compared to cardiac m yocytes. In contrast, changes of pH(i) produced by weak acids or bases produced similar pH(i) responses in both types of cells. It is sugges ted that the differential effects of pH(o) on coronary and cardiac cel ls may be functionally significant, as it will allow rapid alteration of coronary perfusion to meet tissue needs, while maintaining cardiac output.