The role of lysosomes in the heart.

In many tissues there is strong evidence that lysosomes and lysosomal hydrolytic enzymes play important roles in the normal turnover of tissue proteins and other macromolecules. Alterations in the activities and/or availability of lysosomal enzymes are believed to be responsible for alterations in the rate of degradation of many tissue components. It has also been suggested that abnormal release and activation of lysosomal enzymes during ischemia and other potentially lethal events may contribute to the tissue damage that ultimately ensues. Proof that lysosomes are important in cardiac physiology and pathology has not yet been obtained. Circumstantial evidence tends to link lysosomal alterations with changes in protein degradation following many interventions, but this is not always the case. Ischemia is accompanied by leakage of lysosomal enzymes into the cytosol before signs of irreversible damage have appeared, but this association may be coincidental rather than causal. Investigation in the area of cardiac lysosomes has increased markedly in the past 5-10 years. With the development of improved techniques for measuring lysosomal function in heart tissue, there is every reason to expect major breakthroughs in this area of research in the near future.