The influence of age on the activities of some acid hydrolases in the rat liver and kidney.

The process of senescence is generally held to be one involving degenerative changes. This process is particularly evident in the rat kidney where there is extensive atrophy of the functional elements (Kennedy, 1957). In recent years there have been several reports that in degenerating tissues there is an activation of intracellular hydrolases which have an acid optimum pH, and that the increase is due to a release of these enzymes from the lysosomes. Thus de Duve & Beaufay (1959) showed that the autolysis of the liver induced by complete ischaemia is accompanied by a rapid increase in the free activity of several acid hydrolases; a number of liver poisons produced a similar effect (Beaufay, Campenhout & de Duve, 1959). Brachet, de CrolyBriers & Hoyez (1958) found that there was a similar redistribution of typical lysosomal enzymes in certain involuting embryonic tissues. The present work deals mainly with the changes in the free and bound activities of a typical lysosomal enzyme, acid phosphatase, in the liver and kidney of the rat from infancy to advanced senility. The liver has been included since it shows relatively little degenerative change in senescence (Barrows, Falzone & Shock, 1960). Less-detailed measurements have been carried out on the arylsulphatase B and acid deoxyribonuclease of the kidney. A study has also been made of the changes in the activities of acid phosphatase and arylsulphatase B which occur during the degeneration induced by the complete ischaemia of the kidney.