Radioimmunoassay of inactive creatine kinase B protein in human plasma.
We describe a rapid, sensitive radioimmunoassay for enzymatically inactive creatine kinase B protein (CK-Bi) in plasma. 125I-CK-Bi of high specific activity and good stability was prepared by oxidant-based iodination. A 12 minute first antibody incubation was used. Bound and free antigen were separated by a second antibody system. Large excesses of purified CK-MM from human skeletal muscle did not react in the assay. Cross reactivity to CK-MB purified from the plasma of patients with acute myocardial infarction was negligible. The 95th percentile of plasma CK-Bi in 150 adults was 145 microgram equivalents/ml. Within-assay and between-assay precision ranged from 5% to 9% and 6% to 10%, respectively. Evidence is presented indicating that the assay measures inactive creatine kinase B protein, a protein not measured by current assay systems dependent on biological activity.
D004796:Clinical Enzyme Tests; D003402:Creatine Kinase / Q000037:antagonists & inhibitors / Q000097:blood*; D003429:Cross Reactions; D006801:Humans; D007457:Iodine Radioisotopes; D007527:Isoenzymes; D009132:Muscles / Q000201:enzymology; D009203:Myocardial Infarction / Q000175:diagnosis; D011863:Radioimmunoassay / Q000379:methods
D007457:Iodine Radioisotopes; D007527:Isoenzymes; D003402:Creatine Kinase