The effect of drugs on the rate of proteolysis in Vitro within secondary liver lysosomes

The in vitro hydrolysis rate of intravenously injected 131 I‐albumin inside mouse liver phagolysosomes was studied for this type of secondary lysosome, when incubated at pH 5.0 and 37°C in the presence of different drugs. While vitamin A alcohol and etiocholanone showed inhibitory effects, suitable concentrations of chloroquine activated that intraparticulate hydrolysis. On the contrary cortisone, in various concentrations, did not alter the hydrolysis rate of the labeled albumin. Neither cortisone nor chloroquine modified the inhibitory effect of vitamin A. The hypothesis that the drugs act on the hydrolysis rate because they modify the stability of this type of secondary lysosome is forwarded.