STUDIES ON LYSOSOMES. II. THE EFFECT OF CORTISONE ON THE RELEASE OF ACID HYDROLASES FROM A LARGE GRANULE FRACTION OF RABBIT LIVER INDUCED BY AN EXCESS OF VITAMIN A*

Abstract

Vitamin A acid was fed to young rabbits and the activities of 3 lysosomal hydrolases determined in liver homogenates prepared in 0.25[image] sucrose. An excess of the vitamin in vivo caused an increase in the activities of acid protease, beta-glucuronidase, and acid phosphatase unsedimentable at 15,000Xg. In vitro incubation and ultraviolet irradiation caused a greater release of acid protease and acid phosphatase from granular fractions prepared (between 800 and 15,000Xg) from hypervitaminotic animals than from control fractions. The simultaneous administration of cortisone largely prevented the change of sedimentability and retarded release of hydrolases from granules. Hydrocortisone in vitro also stabilized the granules against the effects of pretreatment with vitamin A. Cartilage slices prepared from the ears of hyper-vitaminotic rabbits released significantly more acid hydrolases into the surrounding medium; extracts of their liver granules caused a reduction in the viscosity of chondromucoprotein.