Myofibrillar adenosine triphosphatase activity in congestive heart failure

Abstract

Myofibrillar adenosine triphosphatase (ATPase) activity from seven failing and nine control hearts was studied. The failing hearts came from patients with a clinical and pathological diagnosis of congestive heart failure following benign essential hypertension. Normal hearts were obtained following traumatic death in otherwise normal subjects with no evidence of pathology. As the MgCl₂ concentration was increased, the myofibrillar ATPase from the failing hearts exhibited a significantly lower rise in activity than that from the normal hearts. Increasing the substrate concentration to 5 mm adenosine triphosphate (ATP) increased the myofibrillar ATPase activity to an optimum of .95 µm/mg/15 min in the normal group and .69/µm/ mg/15 min in the failing group. Further increases in substrate concentration decreased the ATPase activity in both groups. It was concluded that myofibrils from a heart in congestive failure following benign essential hypertension hydrolyze ATP at a slower rate than those from normal hearts. Since myofibrillar ATPase activity and tension development go hand in hand, the decrease in ATPase activity in the failing heart may account for its inability to meet the work load imposed upon it. Thus these experiments offer evidence that a lesion in congestive heart failure may reside in the contractile protein itself.