A molecular biologic approach to cardiac toxicology

Cardioprotective Potential of Aqueous Extract of Fumaria indica on Isoproterenol-Induced Myocardial Infarction in SD Rats

Ischemic heart disease (IHD) treatments and preventions by using plant extract and its phytochemical constituents have achieved considerable attention globally due to its cardioprotective effects. This study is aimed at investigating the cardioprotective and vascular effects of Fumaria indica (F. indica) crude extract on isoproterenol- (ISO-) induced myocardial infarction (MI) in Sprague-Dawley (SD) rats. Rats treated with isoproterenol (85 mg/kg, s.c), administered. Twice at an interval of 24 h showed a significant ST-segment elevation in ECG, edema, and necrosis in histopathology and also in troponin I (cTnI), creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST). Pretreatment with F. indica (10, 30, and 100 mg/kg, p.o) for 21 days significantly reversed the effects of isoproterenol-induced ischemic changes in the ECG, levels of cTnI, CPK, LDH, and AST, and histopathological changes. In isolated rat atrial strips, F. indica induced negative chronotropic and inotropic effects which were not affected by pretreatment with atropine, excluding role of cardiac muscarinic receptors. Cumulative addition of the extract induced a vasorelaxant effect on phenylephrine-evoked contractions in isolated rat aortic rings, which remained unchanged when challenged with _L-NAME, excluding role of endothelial NO. However, extract of F. indica concentration dependently reversed contractions evoked with high K⁺, indicating calcium entry blocking effect. In conclusion, the F. indica extract is a cardioprotective remedy that ameliorates the isoproterenol-induced cardiotoxic effects and reverses cardiac ischemia, and the calcium antagonistic effect might be of useful in the treatment of MI.

Exploration of pharmacological interventions to prevent isoproterenol-induced myocardial infarction in experimental models

High incidences of myocardial infarction associated with high morbidity and mortality, are a major concern and economic burden on industrialized nations. Persistent β-adrenergic receptor stimulation with isoproterenol leads to the development of oxidative stress, myocardial inflammation, thrombosis, platelet aggregation and calcium overload, which ultimately cause myocardial infarction. Therapeutic agents that are presently employed for the prevention and management of myocardial infarction are beta-blockers, antithrombotics, thrombolytics, statins, angiotensin converting enzyme inhibitors, angiotensin II type 1 receptor blockers, calcium channel blockers and nitrovasodilators. In spite of effective available interventions, the mortality rate of myocardial infarction is progressively increasing. Thus, there has been a regular need to develop effective therapies for the prevention and management of this insidious disease. In this review, the authors give an overview of the consequences of isoproterenol in the pathogenesis of cardiac disorders and various therapeutic possibilities to prevent these disorders.

Respiration and mitochondrial ATPase in energized mitochondria during isoproterenol-induced cell injury of myocardium

1. Respiration of mitochondria, membrane potential and mitochondrial ATPase under energized conditions were studied in rat myocardium during cell injury induced by treatment with isoproterenol. 2. Increase in the state 4 rate of respiration and ADP:O ratio, as well as decrease in the state 3 rate and Respiratory Control Ratio (RCR) were found. 3. The optimum pH for RCR and for maximum ATPase activity was shifted to lower values. 4. The state 3 respiration was more sensitive to oligomycin inhibition. 5. The mitochondria showed lower ability to generate membrane potential. 6. An increase in the K0.5 values for catalytic sites II and III of mitochondrial ATPase at pH 7.4 and 5.5 was found. 7. These results are consistent with alterations on the integrity of mitochondrial membrane, and corroborate with the hypothesis of changes on the mitochondrial ATPase during isoproterenol-induced cell injury of myocardium.

Kinetic properties of mitochondrial ATPase during isoproterenol-induced cardiomyopathy

1. The kinetic characteristics of the ATP hydrolysis by membrane-bound and Triton X-100 solubilized mitochondrial ATPase, during the isoproterenol-induced cardiomyopathy, were investigated. 2. An increase in the inhibitory action of the oligomycin, a decrease in the affinity of the ATP binding sites and an increase of both activation energy and rate of thermal inactivation were observed for mitochondrial ATPase. 3. The possibility that the changes described are related to the modifications of the active configuration of mitochondrial ATPase, during the isoproterenol-induced cardiomyopathy, is discussed.

Protective effect of taurine against isoprenaline-induced myocardial damage

The effect of the sulfur amino acid, taurine, was examined on histological and biochemical changes induced by a toxic dose of isoprenaline in chick hearts. Isoprenaline treatment (80 or 240 mg/kg id twice daily for 4 days) caused a dose-dependent increase in heart weight and decrease in myocardial ATP. Isoprenaline administration (240 mg/kg id twice daily) produced necrotic changes in hearts, such as eosinophilic degeneration, myolysis, interstitial oedema, fibrosis, and inflammatory cell infiltration. Substantial accumulation of calcium was also observed. Taurine content of the heart was not significantly decreased. Parenteral administration of taurine (200 mg/day for 7 days) partially protected against these necrotic changes induced by isoprenaline. It is suggested that the protective effect of taurine against isoprenaline-induced myocardial injury might be due in part to the prevention of the massive overloading with calcium which is thought to cause myocardial cell necrosis.