Abstract
This chapter discusses the radioimmunoassay of creatine kinase (CK) isoenzymes. The radioimmunoassay for (CK) isoenzymes was developed to provide a quantitative, specific, and sensitive assay for the diagnosis and assessment of myocardial infarction. Creatine kinase is present primarily in the muscular tissues, and in man it is present abundantly in the skeletal muscle, heart, and to a lesser extent in the brain and gastrointestinal tract. Radioiodine was utilized to radioactively label the CK isoenzymes for subsequent use in the competitive displacement radioimmunoassay. It is found that when 125I was attached to the isoenzymes, by the chloramine-T or lac-toperoxidase method, there was marked loss of both CK enzyme activity and binding activity with antibody. The standard inhibition curve is determined with highly purified unlabeled MB CK over a range of 0.5-17 ng CK. It is suggested that to perform an assay, one must determine the background radioactivity, nonspecific binding in the absence of antibody, binding without inhibitor present, and inhibition of binding with known amounts of the unlabeled inhibitor over a range that is applicable for the unknown samples. © 1981, Academic Press, Inc. All rights of reproduction in any form reserved.