S-100ao protein in serum during acute myocardial infarction.

Concentrations in serum of S100ao protein (alpha alpha form of S-100 protein, which is present at high concentrations in heart muscle) were successively measured by enzyme immunoassay in 21 patients with acute myocardial infarction (AMI) and six with angina pectoris (ANP). Results were compared with measurements of creatine kinase isoenzyme MB (CK-MB) concentrations in the same specimens. Mean S100ao concentrations in sera from 100 healthy adults were 0.12 (SD 0.08) microgram/L. In patients with AMI, S100ao concentrations were 4.74 +/- 5.27 micrograms/L at admission, peaked 8 h after admission (23.5 +/- 27.7 micrograms/L), then decreased gradually. Among nine AMI patients who were admitted within an hour after their attack, eight showed abnormally high concentrations of S100ao in serum (greater than 0.5 microgram/L), whereas only four showed abnormally high CK-MB concentrations (greater than 5 micrograms/L) in sera at the time of admission. Serum S100ao concentrations remained within the normal range in all six patients with ANP; however, serum CK-MB concentrations were increased in two of them. Therefore, serum S100ao is useful not only for detection of AMI but also for differentiating AMI from ANP.