The structural proteins of normal and diseased human myocardium.

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Abstract
Microanalytical techniques were developed for the quantitative determination of actomyosin and collagen from 20 to 30 mg (wet mass) samples of myocardium. Actomyosin is the major contractile protein complex and is, therefore, an index of functional muscle; collagen is the major protein of connective and scar tissue and is, therefore, an index of fibrosis. These proteins were determined in 6 myocardial samples from each of 4 normal, 4 ischemic and 3 hypertrophied human hearts. As determined by electrophoresis in a denaturing medium, the concentration of actomyosin in normal myocardium is 69 .mu.g/mg wet tissue; the concentration in ischemic myocardium is not significantly different from normal, but is approximately 45% higher than normal in hearts with left ventricular hypertrophy. These observations indicate that hypertrophy is not simply an increase in total heart mass but, rather, involves an increase in actomyosin concentration in myocardial tissue as well. Collagen is determined from amino acid analysis of whole tissue for 4-hydroxyproline, an amino acid characteristic of this protein; the concentration of collagen in normal (6.1 .mu.g/mg wet tissue) myocardium are not significantly different from those in hypertrophied myocardium. In focal regions of ischemic hearts, however, collagen is increased 2- to 4-fold. The concentration of collagen in myocardial tissue correlated well (r = 0.947) with the degree of fibrosis determined by conventional histological techniques. This work represents a more direct biochemical determination of contractile protein concentration in whole myocardium and a more direct correlation of the biochemical assay for collagen with histological data than were reported previously.