Altered distribution of lysosomal cathepsin D in ischemic myocardium.

Abstract

A B S T R A C T To determine the influence of cardiac ischemia on the activity and subcellular localization of lysosomal cathepsin D, anesthetized rabbits were subjected to ligation of the circumflex coronary artery. Total enzyme activity remained unchanged throughout the 2-h ischemic period, but the subcellular distribution of cathepsin D, as analyzed by biochemical and immunohistochemical techniques, was altered dramatically. A marked increase in nonsedimentable (i.e., 40,000-g supernate) activity developed by 30-45 min and increased further by 2 h. Simultaneously, the immunofluorescent localization of cathepsin D was also changed significantly.Within 30-60 min after occlusion, the fine, particulate staining observed in control myocytes was replaced by bright fluorescent patches composed of large granules. Many of these structures displayed prominent halos of diffuse fluorescent staining in the neighboring myocytic cytoplasm, apparently outside lysosomes per se. After 2 h, when nonsedimentable activity was maximally elevated, most of the fluorescent particles had disappeared completely. During this same interim there was no detectable change in the distribution of lysosomal cathepsin D within interstitial cells. These results are consistent with the hypothesis that an early feature of cardiac ischemia is the release of cathepsin D from myocytic lysosomes into the cytosol of damaged cells.

Lack of effect of methylprednisolone on lysosomal and microsomal enzymes after two hours of well-defined canine myocardial ischemia.

“…washout of intact proteins, 28 or proteolysis. 29 Nevertheless, when these data for changes in protein per gram of wet weight were examined statistically for an MP treatment effect, no significant differences were found between either the L-ischemia or M-ischemia zones of both untreated 19 and MP-treated groups. Table 3 lists the levels of significance for losses of NAGA and /S-gluc from M-and L-ischemia zones.…”

Lanthanum Probe Studies of Cellular Pathophysiology Induced by Hypoxia in Isolated Cardiac Muscle

“…4 FIGURE 10 TEM of unstained, osmicated section reoxygenated for 1Y2 after 2 h of hypoxia. The muscle was exposed to La during the last hour of reoxygenation.…”

“…These factors include prolonged acidosis (2), release of lysosomal enzymes (3,4), mitochondrial failure (5,6), and certain types of plasma membrane alterations, including severe functional abnormalities in membrane permeability and structural defects in membrane integrity (1,7). Nevertheless, definitive information has not been obtained regarding the mechanism(s) responsible for transition from reversible to irreversible myocardial injury.…”

Influence of methylprednisolone of the sequential redistribution of cathepsin D and other lysosomal enzymes during myocardial ischemia in rabbits.

“…One possible reason for confusion is that most studies have evaluated only a single time-point after initiation of ischemia in a single experimental model, and considerable differences have existed in the various studies between the times studied as well as in the exact nature and degree of the stress imposed. Accordingly, in the present experiments we have sought to define sequential changes in lysosomal properties at multiple times after coronary occlusion in a previously-described animal model (17) that reproducibly creates severe, rapidly progressive ischemic necrosis. We have focused special attention on early changes, during the period when damage is not yet irreversible.…”

“…We have focused special attention on early changes, during the period when damage is not yet irreversible. Analysis of these early changes, which may be subtle, has been facilitated by the use of a newly-available procedure for defining the anatomical distribution of lysosomal cathepsin D by immunohistochemical techniques (17)(18)(19), as well as by the use of conventional analyses of the biochemical distribution of several lysosomal hydrolases.…”