Effects of l- and d-Propranolol on the Ischemic Myocardial Metabolism of the Isolated Guinea Pig Heart, as Studied by 31P-NMR

Abstract

Using 31P nuclear magnetic resonance (NMR) spectroscopy (acquisition time of 3 min), we studied the effects of l- and d-propranolol on the ischemic derangement of myocardial energy metabolism in the isolated perfused guinea pig heart. The myocardial pH and concentration of high-energy phosphate were used as measures of the energy metabolism. Cardiac pH progressively declined during ischemia from 7.41 +/- 0.04 to 7.13 +/- 0.05, 6.91 +/- 0.04, 6.74 +/- 0.04, and 6.61 +/- 0.04 (before ischemia and 3, 6, 9, and 12 min after ischemia, respectively). After 3 min of reperfusion, pH rapidly returned to 7.42 +/- 0.04. Creatine phosphate (CP) and adenosine triphosphate (ATP) contents were reduced, while inorganic phosphate (Pi) contents were increased during ischemia. Whereas CP and Pi contents were restored to the normal values after reperfusion, the recovery of ATP contents was poor. Both l- and d-propranolol (10(-6) M) significantly suppressed the fall of the myocardial pH. Changes in the high-energy phosphate contents were also attenuated by l- and d-propranolol. These results suggest that not only l-propranolol, but also d-propranolol can produce beneficial effects on the ischemic derangements of myocardial energy metabolism.