Coronary microcirculatory factors and cardiac muscle cell injury

Coronary artery ligation with or without reperfusion was carried out in Wistar rats to study the role of coronary microcirculatory factors and membrane permeability alteration of cardiac muscle cell in the evolution of cardiac muscle cell injury by using the fine structural extracellular protein tracer, horseradish peroxidase (HRP). The findings were compared with those obtained in noncoronarogenic myocardial injury models following administration of norepinephrine, a pressor, and isoproterenol, a depressor catecholamine. Following left coronary artery ligation lastingfor 10 and 20 minutes, some of the collaterals in the ischemic zone were perused by the tracer, but the numer of patent capillaries decreased during 60-min ligation. The inhomogeneous involvement of cardiac muscle cells in ischemic injury correlated well with these microcirculatory findings. In comparison to permanent ischemia, an abrupt deterioration of the cardiac muscle cell alteration occured after reperfusion with influx of HRP into the damaged cells. The binding of tracer to myofilaments was, however, a later event as compared to that seen in the catecholamine models. The latter observation implies that, in addition to microcirculatory factors, direct cardiac muscle cell stimulation should also be considered in the evolution of noncoronarogenic myocardial injury.