Electron microscopic studies on isoproterenol-induced myocardial lesion in rats.

Abstract

A fine structural investigation was performed on the myocardial lesion induced by high doses of isoproterenol in rats. The findings in the myocardial cells at the early stage consisted of swelling of endoplasmic reticulum and mitochondria and depletion of glycogen granules. The results suggest that isoproterenol primarily affects endoplasmic reticulum and mitochondria, leading to the impairment of their membranes and metabolism, About 8min. after isoproterenol, electron dense bodies were found in mitochondria, suggesting an accumulation of calcium. Fibroblastic infiltration was noted in damaged myocardial area 6 hours after isoproterenol, and after 24 hours in some cases there occasionally appeared young myocytes which were possibly originated in surviving myocardial cells. Propranolol significantly delayed an appearance of abnormalities in endoplasmic reticulum and mitochondria at the early stage, but it had little influence on the improvement of isoproterenol-induced myocardial damages at the later stage.