Myocardial creatine kinase-MB concentration in normal and explanted human hearts and released from hearts of patients with acute myocardial infarction.

: Using an enzyme immunoassay of creatine kinase (CK)-MB concentration commercially available for diagnosis of acute myocardial infarction (AMI), we studied CK-MB concentrations in myocardium of subjects who died from noncardiac causes and in cardiac explants of patients with either coronary heart disease or cardiomyopathy who underwent cardiac transplantation. Secondly, CK-MB concentrations were measured in serial plasma samples of 93 patients with AMI. By calculation of cumulatively released amounts of CK-MB and cumulatively released activities of CK, aspartate aminotransferase (AST) and alpha-hydroxybutyrate dehydrogenase (HBDH), we obtained values of the proportions in which these quantities were released from the myocardium. Taking a myocardial HBDH activity of 152 U/g as a reference value, the released activities of CK and AST, and the released mass of CK-MB per gram of myocardium were calculated. These values were compared to the corresponding quantities in myocardium of normal hearts and in explanted myocardium. Normal hearts differ from explanted myocardium and from "infarcted" hearts with respect to CK-MB concentration, but not with respect to CK, AST and HBDH activities. The wide range of CK-MB concentrations in normal hearts (1-515 micrograms/g) suggests variable expression of the CK-MB gene. The presence of CK-MB is not confined to cardiac tissue. CK-MB concentration in 12 samples of human skeletal muscle equalled 27 +/- 1 micrograms/g (2.1 +/- 0.5% of total CK activity). In conclusion, the mean concentration of CK-MB in normal hearts is low (139 micrograms/g) with a high variation coefficient (127%), but is high (369 micrograms/g) with a small variation coefficient (31%) in explanted hearts.(ABSTRACT TRUNCATED AT 250 WORDS)