Estimation of infarct size by determination of myocardial 3H-tetracycline accumulation in the coronary ligated rat.

Myocardial infarction was produced in rats by ligation of the left coronary artery. Rats were injected with 3H-tetracycline (50 muCi/kg) i.p., 10 minutes prior to ligation. The rats were killed at various time periods after ligation and the myocardial accumulation of 3H-tetracycline determined in the left ventricle or in whole heart homogenates. CPK was also determined in the myocardium or serum. Myocardial 3H-tetracycline was not significantly elevated in the whole heart homogenates. However, there was a significant increase in 3H-tetracycline in the digests of the left ventricle 6 h post-infarct. This increase correlated very well with serum CPK activity. This suggest that this method could be a useful tool in the estimation of infarct size.