Cytochemistry of myocardial structures related to degenerative processes in spontaneously hypertensive and normotensive rats.

Using electron microscopy and cytochemical techniques we investigated structures which are associated with long-term hypertension and ageing in the myocardial cell of the rat. Lysosomes, demonstrated by acid phosphatase and aryl sulfatase activities, were found mainly in the perinuclear region in young rats. With age these organelles appeared with increasing frequency in other regions of the cell. Spontaneously hypertensive rats (SHR) showed an earlier apparent migration of lysosomes than did normotensive rats (WKY). Our observations indicate that lysosomes were closely associated with autophagic vacuoles, membrane swirls , translucent mitochondria, myelin figures and other structures linked with degenerative events. In the oldest SHR lysosomes, autolysosomes (autophagic vacuoles with lysosomal activity), and degenerative structures were observed in various regions of the myocardial cell. Peroxisomes, as demonstrated by catalase activity, did not seem to be affected by hypertension or age. A number of dense osmophilic structures did not react for any of the enzymes studied; these included myelin figures, mitochondrial inclusions and diffuse dense bodies. Our observations implicate both ageing and hypertension in the enhancement of lysosomes and their end products.