Degradation of cardiac troponin I: implication for reliable immunodetection

We have analyzed by different immunological methods the proteolytic degrada tion of cardiac troponin I (cTnI) in human necrotic tissue and in serum. cT nI is susceptible to proteolysis, and its degradation leads to the appearan ce of a wide diversity of proteolytic peptides with different stabilities. N- and C-terminal regions were rapidly cleaved by proteases, whereas the fr agment located between residues 30 and 110 demonstrated substantially highe r stability, possibly because of its protection by TnC. We conclude that an tibodies selected for cTnI sandwich immunoassays should preferentially reco gnize epitopes located in the region resistant to proteolysis. Such an appr oach can be helpful for a much needed standardization of cTnI immunoassays and can improve the sensitivity and reproducibility of cTnI assays.