A biochemical method for the quantitation of myocardial scarring after experimental coronary artery occlusion

The histologic examination and planimetric evaluation of tissue slices has been so far the only available technique for studying the extent of experimental myocardial infarcts in long-term studies; however, this approach is rather time-consuming when the sample size is large. This study describes a new biochemical method for the quantitation of myocardial scarring, based on the determination of left ventricular hydroxyproline, and collagen content at the end of the healing process. Accordingly, several modifications were introduced into previously existing methods for the assay of hydroxyproline: our method allows a linear estimation of hydroxyproline in the range from 0.5 to 5 micrograms, with a precision of +/- 6.1% and a day-to-day variation of +/- 10.5%. The reliability of this approach for studying infarct size has been verified in rats with coronary artery occlusion divided into a control group and in a treated group receiving nitroglycerin. The animals were killed 21 days after coronary ligation and randomly assigned for infarct size evaluation either to the histologic or the collagen method. By histology infarct size averaged 30.6 +/- 4.8% (mean +/- S.E.M.) of left ventricle (LV) in control rats and 16.2 +/- 5.8% of LV in nitroglycerin-treated animals; by the proposed alternative method left ventricular collagen content was 26.8 +/- 1.0 micrograms/mg of dry weight in control rats and 19.5 +/- 1.2 micrograms/mg of dry weight in nitroglycerin-treated animals; infarct size calculated from collagen content by a simple formula, was 37.4 +/- 2.6% of LV and 22.3 +/- 2.6% of LV, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)