Binding of concanavalin A to isolated hepatocytes and its effect on uptake and degradation of asialo-fetuin by the cells

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Abstract
The binding of 125I-labeled concanavalin A [conA] to isolated rat hepatocytes was studied at temperatures between 4-37.degree. C. At the latter temperature, conA concentrations from 0.01-0.4 mg/ml were used. Binding reached a plateau after 40-60 min, when 28-35% of the conA added was bound to the cells (cell density 8 .times. 106 cells/ml). The rate of uptake of 125I-labeled asialo-fetuin by the hepatocytes was lowered to 30% of control values when the cells were preincubated with 0.1 mg of conA/ml. This decrease could be accounted for by a decrease in the rate of asialo-fetuin binding to the .beta.-galactoside receptor of the cells. The binding capacity of the cells was not influenced by preincubation with conA. Asialo-fetuin degradation was decreased only if conA was present during the uptake of asialo-fetuin by the cells. Subcellular factionation revealed that conA lowered the entry rate of endocytosed asialo-fetuin into the lysosomes. The conA effect on degradation is distinct from its effect on the rate of asialo-fetuin uptake by hepatocytes.