Internalization of wheat germ agglutinin (WGA) by rat pancreatic cells in vivo and in vitro.

The uptake of the lectin wheat germ agglutinin (WGA) by the rat pancreas was studied after intraperitoneal injection of FITC-labelled WGA. Strong fluorescence was seen in the interstitial space of the pancreatic parenchyma and on the basolateral surface of acinar cells after one h. Two or four h after injection there was also a fluorescence inside the acinar cells. After intraparenchymal injection of colloidal gold-labelled WGA into the pancreatic gland in situ or in vitro incubation of isolated rat pancreatic acinar cells with WGA-gold, an internalization of the lectin by receptor mediated endocytosis was observed electron microscopically. Clathrin-coated pits or vesicles could not be observed. The results suggest a direct uptake of WGA from the peritoneum into the gland by diffusion and its binding as well as internalization by the pancreatic acinar cells.