RESUMO
Isoproterenol (ISO) in a single dose of 7.5 mg/kg b.w. i.v was found to produce alterations of cardiac metabolism in dogs. After 2 h, high energy phosphate stores and glycogen were reduced, whereas the levels of lactate, pyruvate, the lactate/pyruvate ratio and myofibrillar ATPase activity were elevated. Ca2+ -accumulation by sarcoplasmic reticulum (SR) and mitochondria were increased (P less than 0.01). After 24 h, a partial recovery in the parameters followed could be observed. Only myofibrillar ATPase activity and the Ca2+ -uptake by SR and mitochondria were lowered. When K,Mg-ASP was administered, i.v. concurrently with ISO, myofibrillar ATPase and Ca2+ -accumulation by SR did not differ from controls 2 h after ISO application. Also the other parameters exhibited a tendency to improve (P less than 0.01), but did not reach control levels. 24 h after ISO application we could observe a similar effect of K,Mg-ASP in the prevention of Ca2+ -overload accompanying metabolic changes.
Assuntos
Ácido Aspártico/análogos & derivados , Coração/efeitos dos fármacos , Miocárdio/metabolismo , Nucleotídeos de Adenina/metabolismo , Adenosina Trifosfatases/metabolismo , Animais , Ácido Aspártico/farmacologia , Cálcio/metabolismo , Cães , Isoproterenol/farmacologia , Magnésio/farmacologia , Masculino , Mitocôndrias Musculares/metabolismo , Miocárdio/enzimologia , Miocárdio/ultraestrutura , Miofibrilas/metabolismo , Potássio/farmacologiaRESUMO
Isoproterenol ISO), in a single dose of 7.5 mg/kg body weight, was found to produce alterations of cardiac metabolism in dogs. After 2 hours, high energy phosphate stores and glycogen were reduced, whereas the levels of lactate and pyruvate, the lactate/pyruvate ratio, and myofibrillar ATPase activity were elevated. Ca2+ accumulation by sarcoplasmic reticulum (SR) and mitochondria were increased (p less than 0.01). After 24 hours, a partial recovery in the parameters studied could be observed. Only myofibrillar ATPase activity and the Ca2+ uptake by SR and mitochondria were lowered. When K+, Mg2+-aspartate (K,Mg-ASP) was administered concurrently with ISO, myofibrillar ATPase and Ca2+ accumulation by SR did not differ from controls 2 hours after ISO application; also, the other parameters exhibited a tendency to improve (p less than 0.01), but did not reach control levels. At 24 hours after ISO application, we could observe a similar effect of K,Mg-ASP in the prevention of Ca2+ overload accompanying metabolic changes.
