Increase of myocardial pH by 1- and d-propranolol during ischemia of the heart in dogs.

Myocardial pH was measured continuously with a micro pH electrode inserted into the left ventricular wall in dogs. Anterior descending coronary flow was reduced to about 1/3 of the original flow by partial occlusion of the coronary artery. Myocardial pH decreased from 7.50--7.60 to 7.06--7.24 after partial occlusion. Drugs were injected intravenously during ischemia of the heart caused by partial occlusion. l-Propranolol (1 mg/kg) reduced heart rate and increased the pH from 7.06 +/- 0.04 to 7.48 +/- 0.04 (P less than 0.01). d-Propranolol (1 mg/kg) reduced heart non-significantly and increased the pH from 7.24 +/- 0.05 TO 7.56 +/- 0.05 significantly (P less than 0.05). In other studies, the effect of l- and d-propranolol on both heart rate and metabolic responses to isoproterenol (500 micrograms/kg i.p.) was studied. Isoproterenol increased heart rate and also elevated the blood levels of glucose and lactate. l-Propranolol inhibited these responses to isoproterenol. d-Propranolol did not inhibit the heart rate response but inhibited the blood lactate response to isoproterenol significantly. The blood glucose response to isoproterenol was inhibited by d-propranolol non-significantly. The action of both l- and d-propranolol on ischemic myocardial pH may be related to their action on cardiac metabolism as well as to their local anesthetic action.