PERMEABILITY ALTERATION OF SARCOLEMMAL MEMBRANE IN CATECHOLAMINE-INDUCED CARDIAC-MUSCLE CELL INJURY - INVIVO STUDIES WITH FINE-STRUCTURAL DIFFUSION TRACER HORSERADISH-PEROXIDASE

Abstract

Cardiac muscle cell injury was produced in male Sprague-Dawley rats weighing 300-450 g with the catecholamines, norepinephrine and isoproterenol; sarcolemmal membrane alteration was tested in vivo using the extracellular macromolecular tracer, horseradish peroxidase. Norepinephrine was administered in continuous i.v. infusion in a dose of 4-6 .mu.g/100 g of body weight per min, whereas isoproterenol was given as a single s.c. injection in a dose of 8.5 mg/100 g of body weight. Horseradish peroxidase was injected i.v. and localized in the right ventricular myocardium following 6 and 30 min of circulation time by light microscopy and EM. As early as 10 min after norepinephrine infusion, horseradish peroxidase appeared within cardiac muscle cells possessing normal fine structure. Selective deposition of the tracer on normal and altered myofilaments was noted. Similar observations were made in the isoproterenol model at 60-90 min. Sarcolemmal membrane permeability alteration is an early event in catecholamine-induced cardiac muscle injury. The possible functional significance of the findings is discussed.