Liver lysosomal enzymes in rats during long-term dietary restriction. 1. Changes during the developmental period of life.

The specific activities of the lysosomal enzymes acid phosphatase, beta-galactosidase, arylsulphatase B and cathepsin D were determined in homogenates of livers of rats fed ad libitum and of rats subjected to long-term dietary restriction (10%, 30% and 50% of diet consumed by the ad libitum group). Dietary restriction began soon after weaning and animals were sacrificed 3, 9, 15 and 24 weeks later. Dietary restriction influenced all four enzymes but the changes depended on the enzyme as well as on the degree and duration of the dietary restriction. Total activity of acid phosphatase increased significantly at 3 weeks of restriction but only in the 50% group. The activity returned to normal values at 9 weeks. Arylsulphatase B increased in all experimental groups with a more pronounced change observed at 3 weeks and in the more severely restricted rats. No notable change in the activities of beta-galactosidase and cathepsin D activities was observed. Changes in the liver ultrastructure paralleled the biochemical changes seen at 3 weeks. Numerous autophagic vacuoles and dense bodies resembling age pigments were formed in the hepatocytic cytoplasm. Mitochondrial enlargement, increased matrical density and rough endoplasmic reticulum fragmentation were also noted. Few of these changes were observed at 9 weeks, and the hepatocyte's morphology was virtually normal at 15 and 24 weeks. The marked changes seen at 3 weeks may be a manifestation of the body's adaptive processes to the nutritional stress.