ИСТИНА

Blood measurement of cardiac troponin I (cTnI) is one of the most reliable methods of acute myocardial infarction (AMI) diagnosis. It was shown that cTnI in the blood of patients is presented by the intact molecule and a repertoire of proteolytic fragments. Proteolytic degradation may have a significant influence on the precise immunodetection of cTnI. In this study we aimed to border the cTnI fragments present in the blood of AMI patients. Serial blood samples were collected from 9 patients over a period of 5-36 hours following the onset of AMI. cTnI and its fragments were extracted from blood samples by means of affinity chromatography, studied by Western blotting followed by immunostaining with monoclonal antibodies (mAbs) specific to different cTnI epitopes. A similar set of cTnI forms was found in the blood of different AMI patients. It consisted of the intact cTnI molecule and 11 major fragments with relative molecular mass of 14-24 kDa. mAbs, the epitopes of which lie approximately between 23-158 amino acid residues (aar), stained more than 90% of all detected protein independently of the time when the blood sample was collected. The ratio of different fragments remained constant 5-36 hours after the onset of AMI. We can conclude that the qualitative composition of cTnI fragments in the circulation is constant for 1.5 days following AMI, and almost all detected fragments comprise 23-158 aar of cTnI. Therefore, the region 23-158 aar of cTnI is a preferable target for the antibodies to be used in cTnI immunoassays.