Analysis of ultrastructural changes in the myocardium of rats during withdrawal syndrome after gradual decreasing of metipranolol doses.

Hypersensitization of the myocardium occurring in rats after remission of metipranolol's beta-blocking effect in experiments manifested itself by marked proliferation of the mitochondrial apparatus of myocytes accompanied by an increase in SDH activity as well as its ultrastructural pattern return to control values after a shorter period of A characteristic feature of the withdrawal syndrome occurring in the myocardium of rats exposed to stress following discontinuation of premedication with metipranolol, is partial damage to the mitochondrial apparatus of myocytes associated with a decrease in SDH activity and presence of hyperactive nuclei. Based on the results obtained, the author concludes that, while the withdrawal syndrome sets in during gradual decrease in long-term metipranolol doses in the rat myocardium on stress, it lasts shorter than after sudden interruption of treatment, and myocardial metabolism as well as its ultrastructural pattern return to control values after a shorter period of time.