[Creatine kinase and creatine kinase isoenzyme MB: determination of normal values and values for myocardial infarct, using the new, optimized method with N-acetyl cysteine as the activator (author's transl)].

Preliminary results are reported for the determination of creatine kinase and its isoenzyme MB in healthy individuals and in patients with acute, transmural myocardial infarct, using N-acetyl cysteine as the activator of the enzyme. In healthy individuals, the upper normal limit for creatine kinase activity was 54 U/l; the decision level for the presence of creatine kinase MB activity 9 U/l. The limiting values were only slightly different from those for the GSH-activated creatine kinase, and the results with the old and new methods showed a linear relationship with a slope of 1.0. The differences in the activation of creatine kinase MM by GSH and by N-acetyl cysteine are discussed; the activities obtained for creatine kinase and creatine kinase-MB by the GSH-activation method cannot simply be recalculated to give the appropriate values of the N-acetyl cysteine activation method.