Protective effects of [beta]-adrenergic blockade in isolated ischemic hearts

Abstract

The protective effects of the [beta]-adrenergic blocking drugs, propranolol and atenolol, were tested in a model of global ischemia and assessed electron microscopically. Cat isolated hearts were perfused retrogradely with arterial blood drawn from donor cats. After a period of equilibration, isolated hearts rendered globally ischemic for 1 h and subsequently reperfused for another hour. Hearts were then flushed with physiological salt solution followed by perfusion-fixation with cacodylate-buffered glutaraldehyde, containing ionic lanthanum. Lanthanum was included as a probe of myocardial membrane integrity. Left ventricular subendocardial samples were processed and examined electron microscopically. Nontreated hearts, which underwent normothermic ischemic and reperfusion, displayed extensive ultrastructural damage. Nonischemic and donor cat control myocardial tissue appeared normal in all respects. Hearts that received either propranolol or atenol maintained their ultrastructural integrity, resembling controls. Ionic lanthanum proved to be reliable as a marker of membrane integrity and permeability, as nontreated hearts displayed intracellular deposition of the marker, indicating that deteriorations of membrane integrity occurred. The results suggest that [beta]-adrenergic blockade may be valuable in preserving myocardium subjected to ischemia and reperfusion.