THE EFFECT OF VARIATIONS OF pH UPON THE ACTIVATION OF PHOSPHORYLASE BY EPINEPHRINE IN PERFUSED CONTRACTING HEART, LIVER SLICES AND SKELETAL MUSCLE

¹ Departments of Anesthesia and Pharmacology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The effect of variations of pH upon epinephrine activation of phosphorylase was studied in isolated perfused rat hearts as well as in diaphragms and liver slices incubated in vitro. The action of epinephrine upon phosphorylase was significantly enhanced in all three tissues by an increase of pH from 6.9 to 7.8. In the perfused heart, the increase in the metabolic effect of epinephrine with a rise in pH was associated with an increase in the inotropic action of the hormone. In diaphragm, an increase in pH alone caused a rise in phosphorylase activity which could not be blocked by adrenergic blocking agents but was dependent upon the presence of calcium in the incubation media. Pretreatment of rats with dichloroisoproterenol blocked the action of epinephrine upon diaphragm phosphorylase at pH 7.8 and 6.9. In liver slices, epinephrine activity was enhanced by an increase of pH, but the action of cyclic 3',5'-adenosine phosphate was unaffected by the same change in hydrogen ion concentration.