Isolation and characterization of autolysosomes which appeared in rat liver after leupeptin treatment

Autolysosomes were isolated from rat livers treated with leupeptin by a combination of differential and Percoll density gradient centrifugation techniques. The purified autolysosome fraction was verified by morphological analysis to be highly purified and to contain contaminants which were scarcely detectable. The enrichment of the lysosomal enzyme activities in the purified autolysosomes over the homogenate was 12-, 14-, 22-, and 24-fold for beta-glucuronidase, acid phosphatase, beta-N-acetylglucosaminidase, and cathepsin D, respectively. Measurement of the activity of the marker enzymes for various subcellular organelles also proved that the purified autolysosome fraction was essentially free from contamination by other organelles. When the autolysosomes isolated from rat livers treated with leupeptin for 1 h were disrupted by osmolysis, acid hydrolases were easily solubilized. Acid phosphatase, however, became membrane bound in the autolysosomes prepared at longer periods of time after the leupeptin treatment. The autolysosomes exhibited enhanced permeability of the membranes after a short duration of time after the leupeptin treatment (30 and 60 min) and became stabilized later. These changes in the properties of the autolysosomes with time after the leupeptin treatment may be interpreted as meaning that progressive rearrangement of the lysosomal constituents occurred within the autolysosomes with time after the genesis.