We have analyzed by different immunological methods the proteolytic degradation of cardiac troponin I (cTnI) in human necrotic tissue and in serum. cTnI is susceptible to proteolysis, and its degradation leads to the appearance of a wide diversity of proteolytic peptides with different stabilities. N- and C-terminal regions were rapidly cleaved by proteases, whereas the fragment located between residues 30 and 110 demonstrated substantially higher stability, possibly because of its protection by TnC. We conclude that antibodies selected for cTnI sandwich immunoassays should preferentially recognize epitopes located in the region resistant to proteolysis. Such an approach can be helpful for a much needed standardization of cTnI immunoassays and can improve the sensitivity and reproducibility of cTnI assays.

Two groups of monoclonal antibodies (MAbs) specific to human cardiac troponin I (cTnI) were generated by immunization of mice by isolated cTnI (group I, 16 MAbs) or by the whole troponin complex (group II, 15 MAbs). Two sets of overlapping decapeptides covering the complete sequence of cTnl were prepared and used for epitope mapping by SPOT technique. Majority of MAbs (28 out of 31) interacts with synthetic peptides thus indicating that they recognize liner epitopes. MAbs raised against isolated cTni preferentially recognize epitopes located at the N-or C-terminal ends of cTnI. Nine out of fifteen MAbs raised against whole troponin complex interact with epitopes located in the N-terminal part of cTnI. Generation of MAbs recognizing both isolated cTnI and cTnI inside of troponin complex and mapping their epitopes provides reliable detection of TnI in serum of patients with acutc myocardial infarction. BIOCHEMISTRY and MOLECULAR BIOLOGY INTERNATIONALstructure of skeletal and cardiac TnI [4,5]. This makes possible production of cTnl specific antibodies which can be used for detection of many types of myocardial cells damage [6,7]. After cell death caused by infarction cTnI is released into the extracellular space and 4 -6 hours after onset of the chest pain can be detected in the blood stream [8,

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