Studies on the lysosomal enzyme system of the liver in rats undergoing swimming training.

Lysosomal acid phosphatase, beta-glucuronidase, and cathepsin-D were studied in liver cell fractions of rats regularly exercised by swimming. On the 21st day of the training, enzyme activities in the extralysosomal fraction and in the lysosomal fraction were higher and lower, respectively, than in the untrained controls. On the 40th day an increased enzyme activity was found in both fractions. By the end of the training period (54th and 80th days), a slightly decreased activity was recorded in both fractions. Lysosomal membrane permeability for enzymes was higher during the first period of the training, in particular when estimated under hypotonic conditions. Regular swimming training or 12-day treatment by ACTH stabilized the membrane of the liver lysosomes. This stabilization was believed to be mediated by corticosteroids mobilized by exercise or by the administration of ACTH.