Release kinetics of cardiac troponin T in coronary effluent from isolated rat hearts during hypoxia and reoxygenation

Summary

A newly developed troponin T (TnT) test for the detection of myocardial cell necrosis has been reported to be very efficient in the detection of acute myocardial infarction. The aim of the present study was to determine whether cardiac TnT in coronary effluent from isolated heart perfused with albumin-free perfusion medium could be detected using the enzyme-linked immuno-sorbent assay developed by Katus et al. Isolated rat hearts were perfused according to the method of Langendorff. Coronary flow rate was measured by timed collection of the coronary perfusate that dripped from the hearts during 5 h of hypoxia (protocol A) or 4 h of hypoxia followed by 1 h of reoxygenation (protocol B). Creatine kinase (CK) and lactate dehydrogenase (LD) levels were compared with that of TnT. Myocardial adenine nucleotides were measured by HPLC. There was a strong correlation between TnT levels in albumin-free coronary effluent and TnT levels in coronary effluent diluted 1:1 with 5% bovine serum albumin (r=0.996, N=72). The coefficients of correlation between TnT and CK or LD during hypoxia and reoxygenation were 0.891 (N=88) and 0.871 (N=88), respectively. The coefficient of correlation between CK and LD was 0.993 (N=88). There were no significant differences in either the decrease of coronary flow or the increase of TnT content between the hearts in the two protocols. There was no significant correlation between ΣTnT and energy charge of adenine nucleotides. These results indicate that cardiac TnT levels can be easily measured in albumin-free coronary effluent of isolated heart preparations. Like CK and LD, TnT is a good indicator for detecting myocardial cell damage. However, the release kinetics of TnT seem to be different than those of CK and LD. After 4 h of hypoxia, 1 h of reoxygenation has no effect on coronary flow rate or release of TnT. ΣTnT did not determine energy charge at the end of hypoxia or reoxygenation.