REVERSAL OF IMPAIRED OXIDATIVE-PHOSPHORYLATION AND CALCIUM OVERLOADING IN THE IN-VITRO CARDIAC MITOCHONDRIA OF CHF-146 DYSTROPHIC HAMSTERS WITH HEREDITARY MUSCULAR-DYSTROPHY

Membrane-mediated excessive intracellular calcium accumulation (EICA), and diminished cellular energy charge are invariably present in the myocardium of CHF-146 strain dystrophic hamsters (DH) with hereditary muscular dystrophy (HMD) and hypertrophic cardiomyopathy (HC). Therefore, we investigated respiratory dysfunctions and Ca2+ overloading in the isolated cardiac mitochondria from young and old DH, and whether these abnormalities can be reversed by controlling EICA in the in vitro mitochondria upon chelating excessive Ca2+ from the isolation medium with EDTA. Age- and sex-matched CHF-148 strain albino normal hamsters (NH) served as the disease controls. As an index of membrane-mediated EICA and chronic cellular degeneration, Ca and Mg concentrations were quantitated in the ventricular myocardium and in the cardiac mitochondria harvested in two different isolation media. Mitochondria from young and old DH, isolated in the absence of 10 mM EDTA (B0 medium), revealed poor coupling of oxidative phosphorylation, diminished stimulated oxygen consumption rate, and lower respiratory control and ADP/O ratios, than those seen in NH. However, incorporation of 10 mM EDTA in the isolation medium (B medium) restored the mitochondrial functions and reduced massive Ca2+-overloading in the dystrophic organelles. Ca concentration in the in vitro mitochondria from DH was significantly higher than in NH, irrespective of the composition of the isolation medium and age of the hamsters. Furthermore, the dystrophic organelles isolated in B medium had a much lower Ca concentration, and markedly improved oxidative phosphorylation as seen in the cardiac mitochondria from NH, compared to those prepared using B0 medium. Tissue Ca levels in the hearts of both young and old DH were also significantly elevated compared to their normal counterparts, bearing a positive correlation with the intramitochondrial Ca2+-overloading in DH. However, Mg levels in the myocardium and cardiac mitochondria were similar in NH and DH. These data suggest that mitochondrial dysfunctions and Ca2+-overloading in HMD with HC may be reversible, if membrane-mediated EICA in the dystrophic myocardium is pharmacologically mitigated by a potent Ca2+-channel blocker.