Detection of Cardiac-Specific Creatine Kinase lsoenzyme in Sera with Normal or Slightly Increased Total Creatine Kinase Activity

We describe a spectrophotometric kinetic assay for de-tecting creatine kinase MB isoenzyme activity in the 1 to 10 U/liter range. The MB isoenzyme was isolated [C/in. Chem. 20, 36 (1974)] and assayed (Rosalki method) with an Abbott ABA-100. Good reproducibility was dem-onstrated for MB isoenzyme activities near 1 U/liter (CV = 2.6%). Sera with normal or slightly increased total creatine kinase activity were evaluated. Sera of 14 pa-tients with acute myocardial infarction contained, per liter, 84 to 236 U of total creatine kinase activity and 4.6 to 28.0 U of isoenzyme MB activity; corresponding ranges for sera from healthy lab technicians and pa-tients with noncardiac disease were 36 to 277 and 0 to 2.6 U. MB isoenzyme activity for infarction patients rose and fell sharply within three days after the infarction. Atypical time-course patterns, MB isoenzyme activity remaining abnormally great for five days, were ob-served in serum from patients with prolonged atrial f i-brillation and congestive heart failure or cardiomyopa-thy; the BB isoenzyme (ito 5 U/liter) was also detected in sera of such patients but was absent in sera from in-farction patients. Quantification of column-isolated MB by the assay described is rapid, easy, specific, and ex-tremely sensitive for measuring MB in the 1 to 10 U/liter range. Addftlonal Keyphrases: diagnostic aids #{149}myocardial in-farction #{149}chromatography on DEAE-Sephadex #{149}tachy-arrythmia #{149}heart disease #{149}muscular dystrophy #{149}p0-lymyositis #{149}kinetic enzyme assay #{149}changes observed in other disorders An earlierreport from this laboratory described the use of a column chromatographic technique for separating serum CK1 isoenzymes (1). CK isoen