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Cardiac Troponin T (cTnT) is a cardiac structural protein which is released in the circulation during myocardial cell damage. In this study we addressed the question of whether beta-sympathomimetic induced myocardial cell damage in rats can be detected in blood by the TROPT sensitive rapid test strip which is primarily manufactured for the detection of acute myocardial infarction in humans. Sixteen male rats and 16 female animals were treated once with orciprenalinesulphate s.c. to induce tachycardia. The control group which consisted of 16 rats of both sexes received vehicle (physiological saline). The heart rate of two groups of 10 rats (5 of each sex) was measured after orciprenaline or saline treatment. After 1-2 hours we could demonstrate an increased heart rate in the orciprenaline group. Furthermore in this group we could show elevated cTnT levels in peripheral blood measured with the enzyme-linked immunosorbent assay (ELISA) Enzymun-Test Troponin T for troponin T and a positive reaction of the TROPT sensitive test strip. When compared with the ELISA method, the test strip showed a positive reaction at cTnT levels of 0.64 ng/ml upwards. After 24 hours and 96 hours half of the animals were sacrificed for histological examination of the heart tissue. After 24 hours all orciprenaline treated and examined animals showed myofibrillar degeneration of the myocardial cells. The second half of the animals sacrificed 96 hours after treatment with the sympathomimetic drug showed reparative fibrosis of the myocardium. All animals with myocardial damage due to orciprenaline showed a positive test strip result 2 hours after injection. Twenty-four hours after injection only 8 of the 16 animals had a positive test strip result although histological cell damage was demonstrated. All animals treated with physiological saline had negative results of the test strip and showed no signs of myocardial cell damage. We conclude that the TROPT sensitive test strip is a rapid and reliable screening tool for detecting myocardial cell alteration in rats without the need of an expensive and time-consuming ELISA procedure if it is used in early phases of the experiment because all animals with myocardial damage were identified by the test 2 hours after induction of the damage. If the time range between the induction of the injury and the use of the test strip or the ELISA procedure is too wide, in our experiments 24 h, false negative results may occur.

A cardioselective parameter has been available for about 2 years since the development by KATUS of an immunoassay for cardiac Troponin T (TnT). The major advantages of this TnT assay are its cardiospecificity and its sensitivity. The parameters usually determined in toxicity studies in rats to detect alterations in the myocardial cells, e.g. aspartate aminotransferase (ASAT), creatinine kinase (CK) and lactate dehydrogenase (LDH), are either of low sensitivity in this species or give falsely high results as the consequence of stress or haemolysis. We therefore investigated in the present study how well Troponin T, determined with the ELISA Troponin T from Boehringer Mannheim, can detect experimentally induced myocardial lesions in rats. In order to achieve hypoxic damage of the cardiomyocytes in these experiments in rats, male Sprague-Dawley rats were given two doses of 4 mg/kg isoprenaline each (Aludrin from Boehringer Ingelheim, FRG) subcutaneously. The second dose was given 7 h after the start of the experiment. Serum samples were analysed for Troponin T (TnT) levels and, for comparison, aspartate aminotransferase (ASAT), creatine kinase (CK), and lactate dehydrogenase (LDH). Histological examinations of the heart muscle were performed 24 and 96 h after the first injection. As expected, histological examinations of the isoprenaline-treated animals revealed marked myofibrillic degeneration of the myocardium 24 h after the first injection. Markedly elevated serum TnT levels (up to 7.9 ng/ml) were already evident in these animals after 6 h. TnT values decreased with time, but were still statistically significant after 48 h. Of the well-established indicators for diagnosing myocardial infarction, only ASAT showed transient statistically significant increases over 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)