Quantitative assessment of infarct size in isoproterenol-infarcted rats

The authors performed a number of experiments aiming at quantifying the infarct size in Sprague-Dawley male rats. The experimental model employed was isoproterenol (ISP) induced, infarctlike myocardial lesions. In quantifying the extent of the infarct area they compared the cross reliability of enzymatic and histological methods. ISP was administered in two subcutaneous injections (50 mg/100 Gm body weight) at a 24 hour interval. At the peak of the necrotic process (48 hrs after the first injection), the heart was subjected to enzymatic or histological studies. Thus, a group of infarcted animals (n = 25) and their controls (n = 15) underwent the assessment of creatine kinase (CK) content in the homogenate of the myocardium. Another group of animals (n = 15) was used for histological observations, including measurement of infarct size by planimetry from histological sections. A good relationship was observed between the percentage of necrotic tissue calculated on the basis of CK values (69.11 +/- 2.39%) and the infarction area assessed by planimetry (72.37 +/- 2.69%) (mean +/- standard error of the mean [SEM]). Thus, the present study confirms that ISP-induced myocardial lesions are a simple and reliable model for experimental infarct. Moreover, the assessment of the CK content in the heart is correlated with histological studies by planimetry, and is suggested as a direct enzymatic method to quantify the extent of myocardial necrosis.