Ultrastructural and lysosomal enzyme studies of skeletal muscle and myocardium in rats with long-term vitamin E deficiency

Abstract

Muscular dystrophy and cardiomyopathy were produced in weanling rats by feeding a vitamin E-deficient diet for 12 mth. Deficient and control rats were killed, and skeletal muscle and myocardium were used for subcellular studies and biochemical assay of selected lysosomal enzymes. Ultrastructurally, the skeletal muscle showed various degrees of pathological changes. In the severely damaged muscle fibres, prominent increase of secondary lysosomes, autophagic vacuoles, residual bodies, disappearance of myofilaments, rupture of sarcolemma and shrinkage of muscle fibres were noted. The damaged muscle fibres finally became dense residual bodies and dispersed in the interstitial spaces, where the macrophages and fibroblasts were found. In the myocardium, some muscle fibres were intact with mild fatty infiltration and marked proliferation of mitochondria. However, in the severely damaged myocardial fibres, the whole fibre was always filled with amorphous dense bodies, and the sarcolemma was ruptured. This resulted in dispersion of many cellular organelles in the surrounding interstitial space. A significant increase of cathepsin and beta-glucuronidase activity in the cytosol of both organs suggests that lysosomal enzymes may play a major role in the destruction of muscle and cardiac fibres in the long-term vitamin E-deficient animals.