抄録
Twenty-two cat hearts were perfused according to Langendorff technique and myocardial regional ischemia was induced by occlusion of left anterior coronary artery. Separation of particulate (bound) from soluble (free) fraction, and subsequent fractionation into plasma membranes, lysosomes, sarcoplasmic reticulum, and mitochondria were performed by sucrose density gradient ultracentrifugation. By ischemia for 60min, particle bound activity of cathepsin D decreased from 4.2±0.24U/mg protein to 3.2±0.31U/mg protein (p<0.01). Likewise, the particle-bound activity of β-glucuronidase decreased from 11.9±0.92U/mg protein to 6.2±128U/mg protein (p<0.01). Accordingly, free/bound activity ratios of cathepsin D increased from 0.8 to 1.9 and β-glucuronidase from 0.9 to 2.8, respectively. Conspicuous fall from 12.8±0.6U/mg protein to 8.0±0.97U/mg protein (p<0.01) in absolute specific activity of cathepsin D bound to the lysosomal fraction, presents definitive evidence of lysosomal release of the acid hydrolases during the early phase of myocardial ischemia. Electron microscopic observation of the ischemic myocytes revealed ultrastructural alterations of the lysosomes suggestive of autophagic degradation of various subcellular organelles
