Attenuation of ischaemia-induced regional myocardial acidosis by bevantolol, a beta 1-adrenoceptor antagonist, in dogs.

In dogs anaesthetized with pentobarbital, the left anterior descending coronary artery (LAD) was occluded for 90 min. so that about 1/2 of the original flow was allowed to flow (partial occlusion). Bevantolol (a beta 1-adrenoceptor antagonist) or propranolol (a reference drug) was injected intravenously 30 min. after partial occlusion. Regional myocardial pH was measured by a micro glass pH electrode inserted in the LAD area. Partial occlusion decreased myocardial pH by 0.62 to 0.74. Bevantolol (1.0 mg/kg) or propranolol (1.0 mg/kg) significantly increased myocardial pH, that had been decreased by partial occlusion, within 60 min. after the injection. Restoration of myocardial [H+] (defined as return towards a lower [H+] to the preocclusion level) (calculated from the pH data) induced by bevantolol and that induced by propranolol were 64.0 and 66.4% (measured 60 min. after the injection), respectively. Bevantolol or propranolol decreased heart rate also. Even in the paced heart, bevantolol restored the myocardial [H+] that had been increased by partial occlusion. These results suggest that bevantolol has a favorable effect on the ischaemic myocardium as has propranolol, and that the pH effect of bevantolol is not primarily due to a decrease in heart rate.