Histochemical investigation of myocardial proteases in heart anoxia, under protection with cardioplegic solution and protease inhibitors.

We studied the histochemical behaviour of neutral non-lysosomal and acid lysosomal proteases of the myocardium in heart anoxia by aorta-clamping, using an experimental model alike to the open heart surgery conditions. After one hour of blood deprivation we found destabilization, conglomeration, diffusion and extracellular release of the histochemical reactions for neutral BANA-reactive proteases, cathepsin B, acid and neutral gelatinases in monkey, rat and mice myocardium, in connection with lytic ultrastructural lesions. Intracardiac perfusion with cardioplegic solution exerted a partial protective effect which is improved by adding Trasylol, a protease inhibitor. Administration of Trasylol by intravenous injections preceding aorta clamping, or/and by intracardiac perfusion after aorta clamping, normalized the histochemical reactions of proteases together with the ultrastructural organization of the myocardial fibres. Acting especially by the inhibition of membrane serine proteinases, Trasylol may intercept membrane permeabilization events, impairing the proteolytic cascades triggered by anoxia.