DIAGNOSTIC EFFICIENCY OF TROPONIN-T MEASUREMENTS IN RATS WITH EXPERIMENTAL MYOCARDIAL-CELL DAMAGE

A cardioselective parameter has been available for about 2 years since the development by KATUS of an immunoassay for cardiac Troponin T (Tn T). The major advantages of this TnT assay are its cardiospecificity a nd its sensitivity. The parameters usually determined in toxicity stud ies in rats to detect alterations in the myocardial cells, e.g. aspart ate aminotransferase (ASAT), creatinine kinase (CK) and lactate dehydr ogenase (LDH), are either of low sensitivity in this species or give f alsely high results as the consequence of stress or haemolysis. We the refore investigated in the present study how well Troponin T, determin ed with the ELISA Troponin T from Boehringer Mannheim, can detect expe rimentally induced myocardial lesions in rats. In order to achieve hyp oxic damage of the cardiomyocytes in these experiments in rats, male S prague-Dawley rats were given two doses of 4 mg/kg isoprenaline each ( Aludrin(R) from Boehringer Ingelheim, FRG) subcutaneously. The second dose was given 7 h after the start of the experiment. Serum samples we re analysed for Troponin T (TnT) levels and, for comparison, aspartate aminotransferase (ASAT), creatine kinase (CK), and lactate dehydrogen ase (LDH). Histological examinations of the heart muscle were performe d 24 and 96 h after the first injection. As expected, histological exa minations of the isoprena line-treated animals revealed marked myofibr illic degeneration of the myocardium 24 h after the first injection. M arkedly elevated serum TnT levels (up to 7.9 ng/ml) were already evide nt in these animals after 6 h. TnT values decreased with time, but wer e still statistically significant after 48 h. Of the well-established indicators for diagnosing myocardial infarction, only ASAT showed tran sient statistically significant increases over 24 h. The activities of CK and LDH did not show any sensitive increases during the 96-h inves tigation period. On examination of the animals sacrificed 96 h after i nduction of myocardial damage with isoprenaline, no signs of acute myo cardial degeneration were found in any of the animals. They displayed marked formation of reparative fibrosis. At this time, the TnT serum l evels of all animals investigated were within the range of the control animals. Data from this study show that ELISA Troponin T is useful fo r sensitive and specific detection of myocardial damage in the rat. In this species, which is used for both pharmacological and toxicologica l experiments of varying lengths, it is possible to determine cardiac damage during the in-life phase by measurement of Troponin T.