Creatine Kinase System in Failing and Nonfailing Human Myocardium

Abstract

Background The creatine kinase (CK) reaction is important for rapid resynthesis of ATP when the heart increases its work. Studies defining the CK system in human failing and nonfailing myocardium are limited and in conflict. To resolve this conflict, we measured the activities of CK and its isoenzymes and the contents of creatine and CK-B in homogenates of human myocardium. Methods and Results Myocardium was sampled from 23 subjects who underwent heart transplant, 36 subjects maintained in an intensive care unit before heart harvesting, 13 accident victims, and 2 patients undergoing heart surgery. Since the characteristics of myocardium of potential organ donors differed from those of myocardium of accident victims, data are presented for three groups: failing, donor, and control. CK activity was 7.7±1.9 and 6.0±1.4 IU/mg protein in left (LV) and right (RV) ventricles of failing, 9.4±2.5 and 10.7±2 IU/mg protein in LV and RV of donor, and 11.6±2.4 IU/mg protein in LV of control hearts. CK-MM and the mitochondrial isoenzyme activities were lower in failing and donor LV, and CK-MB activity and CK-B content were higher in failing and donor hearts. Creatine contents were 64±25 and 56±18.6 nmol/mg protein in LV and RV of failing, 96±30 and 110±24 nmol/mg protein in LV and RV of donor, and 131±28 nmol/mg protein in LV of control hearts. Conclusions In failing and nonfailing donor human myocardium, there is a combined decrease of CK activity and creatine that may impair the ability to deliver ATP to energy-consuming systems.