Renal lysosomal protein digestion in experimental lipidosis

The present study was undertaken to clarify whether or not chlorphentermine-induced lipidosis in the proximal tubules of the rat kidney interferes with lysosomal degradation of an absorbed exogenous protein. 125I-lysozyme was injected in vivo; its degradation was measured in vitro using slices from renal cortex. The subcellular distribution of the protein was examined by electron microscope autoradiography. Lysosomes structurally altered by the lipidosis were able to accumulate the protein, although to a smaller extent than normal-appearing lysosomes present in the same cells; the label persisted longer in the altered than in the normal-appearing lysosomes. Protein degradation was significantly decreased in renal cortical slices from chlorphentermine-treated rats compared with controls. The results indicate that experimentally-induced lipidosis is associated with decreased proteolytic efficiency of the lysosomes in proximal tubules.