beta-adrenergic receptors and intracellular signalling pathway in stunned and non-ischemic regions of pig myocardium

The beta -adrenergic pathway may have a role in the pathophysiology of isch emic syndromes characterised by reversible left ventricular dysfunction, su ch as myocardial stunning and other clinical conditions of unstable angina or coronary spasms, or chronic reversible left ventricular dysfunction, whi ch might be a consequence of repeated events of short-term ischemia ("repet itive stunning"). A partial-to-total occlusion of the left anterior descending coronary arter y in pigs was used to induce short periods of ischemia (total ischemic time 12 +/- 2 min). Hypokinesis and dyskinesis of the myocardium were considere d signs of myocardial dysfunction. We found a maintained function of the be ta -adrenergic signalling system. Density and affinity of beta -adrenergic receptors were not different in stunned and non-ischemic regions, nor were cyclic AMP and cyclic GMP intracellular contents and ratio, nor well as the ratio of stimulatory/inhibitory G protein a subunits. Our findings are in agreement with a maintained beta -adrenergic signalling system in the pathophysiology of chronic reversible left ventricular dysfu nction.