Creatine Kinase Isoenzyme MB (CKMB) Controversy: Perimortal Tissue Acidosis May Explain the Absence of CKMB in Myocardium at Autopsy

摘要

In patients with acute myocardial infarction (AMI), the activity of creatine kinase isoenzyme MB (CKMB) in plasma consistently accounts for ～15% of the total CK activity (1)(2). By contrast, the CKMB content of cardiac tissue, although sometimes reported to be consistent with the 15% plasma activity of CKMB (2)(3), has also been reported to be negligible in healthy myocardium (4)(5). In these studies, the higher CKMB found in diseased hearts was thought to reflect cellular adaptation to disease. An alternative explanation for low CKMB is its limited thermostability and susceptibility to pH (6).The objective of the present study was to examine whether inactivation of CKMB, either postmortem or during perimortal tissue acidosis, could explain the absence of CKMB in cardiac tissue at autopsy. The influence of tissue acidosis was studied by exposing heart tissue to pH values of 5.0–7.5. Finally, because myocardial ischemia and tissue acidosis attributable to AMI are located predominantly in the endocardium (7)(8), transmural differences in CKMB content were studied in the hearts of patients who died after AMI.Slices (1 cm), midway between apex and base, were obtained from 20 hearts of patients (11 males and 9 females) who died from noncardiac causes and without history of cardiac complaints. Mean values for age, autopsy delay, and heart length and weight (± SD) were 71 ± 15 years, 29 ± 22 …