ИСТИНА

Ternary troponin complex (ITC­complex) consisting of troponin I, troponin T and troponin C plays a key role in the regulation of muscle contraction. In heart muscle cells, troponin I and troponin T are expressed as tissue­specific cardiac isoforms (cTnI and cTnT, respectively) that makes them essential biomarkers of myocardial injury. The choice and characterization of a standard for immunochemical determination of cardiac troponins is a crucial issue of their laboratory diagnostics. The aim of this work was to compare the stability of recombinant ITC­complex (recITC) and native ITC­complex (natITC) in different conditions. In our study, we incubated both complexes in various matrices at +4, +25, and +37°C for up to 48 hours and then measured troponin immunochemical activity at different time points using monoclonal antibody assays specific to individual troponins or to the whole ternary complex. Comparison of different buffer solutions showed that addition of BSA preserves immunochemical activity and increases stability of both ITC­complexes. At +4°C and +25°C, troponins were stable in the buffer solution, serum, citrate and heparin plasmas for up to 48 hours but partially dissociated in EDTA plasma. Incubation at +37°C led to fast dissociation of cTnT from both ITC­complexes in all matrices, that was most pronounced in heparin and EDTA plasmas. This was accompanied by degradation of cTnT and cTnI in serum and EDTA plasma. Immunochemical activity and stability of recITC was similar to those of natITC in all tested matrices and conditions, that makes it possible to use recITC as an immunochemical standard for the detection of troponins or troponin complexes.