Receptor-linked degradation of /sup 125/I-insulin is mediated by internalization in isolated rat hepatocytes
When hepatocytes were freshly isolated from rat liver and incubated for various periods of time at 37 degrees C, the media from the incubation, when completely separated from the cells, actively degraded /sup 125/I-insulin. THis soluble protease activity was strongly inhibited by bacitracin but was unaffected by the lysosomatropic agent ammonium chloride (NH/sub 4/Cl). When hepatocytes were incubated with /sup 125/I-insulin at 37 degrees C in the presence or absence of 8 mM NH/sub 4/Cl the ligand initially bound to the plasma membrane and was subsequently internalized as a function of time. When hepatocytes were incubated at 37 degrees C for 30 minutes with /sup 125/I-insulin in the presence of bacitracin and NH/sub 4/Cl or bacitracin alone and the cells were washed, diluted, and the cell-bound radioactivity allowed to dissociate, the percent intact /sup 125/I-insulin in the cell pellet and in the incubation media was greater in the presence of NH/sub 4/Cl at each time point of incubation. Under these same conditions a higher proportion of the cell-associated radioactivity was internalized and a higher proportion was associated with lysosomes. The data suggest that receptor-mediated internalization is required for insulin degradation by the cell, and that this process, at least in part, involves lysosomal enzymes. Furthermore, the data demonstrate that internalization is not blocked by the presence of bacitracin or NH/sub 4/Cl in the incubation media, but that degradation is inhibited.
- Research Organization:
- National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
- OSTI ID:
- 6795276
- Journal Information:
- Yale J. Biol. Med.; (United States), Vol. 55:2
- Country of Publication:
- United States
- Language:
- English
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INSULIN
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LABELLED COMPOUNDS
LYSOSOMES
RECEPTORS
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
CELL CONSTITUENTS
CHEMISTRY
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ISOTOPE APPLICATIONS
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