Binding and internalization of 125I-Bolton-Hunter-substance-P by pancreatic acinar cells

Binding of 125I-labelled Bolton-Hunter substance P (125I-BH-SP) to dispersed pancreatic acinar cells from guinea pigs was studied. Association of 125I-BH-SP to acinar cells was rapid, specific, and temperature-dependent. Dissociation of bound 125I-BH-SP was slow and 60 min after dilution only 12% of cell-associated radioactivity had dissociated from cells. Various c-terminal fragments of SP as well as structurally related substances inhibited binding. Bound 125I-BH-SP partly resisted acid washes of cells. After lysis of cells, cell-associated radioactivity was chromatographed on a Sephadex G-25 column. Part of radioactivity was eluted as apparently intact 125I-BH-SP. It is suggested that this material has been internalized into acinar cells.