BETA CELLS ARISE FROM GLUCOSE-TRANSPORTER TYPE-2 (GLUT2)-EXPRESSING EPITHELIAL-CELLS OF THE DEVELOPING RAT PANCREAS

We observe Glut2 protein in day 11 (E11) rat embryos in an erndodesmal domain containing the pancreatic primordium. Glut2 expression continu es as the endodermal epithelium evaginates into the surrounding mesenc hyme to form the pancreatic buds. Cells of the dorsal and ventral panc reatic buds maintain Glut2 expression as the epithelium grows and bran ches to form ducts. As acini form at the ends of the ducts, acinar cel ls cease Glut2 expression. Insulin protein is first detected in small clusters at the interface between pancreatic epithelium and mesenchyme . These clusters disperse into the interstitial tissue between E13 and E17. At E17 a distinct, larger population of insulin-expressing cells arises in the Glut2-expressing ductal network. Insulin- and Glut2-coe xpressing cells then appear to segregate into large aggregates to form the beta cells of the islets of Langerhans. These observations suppor t the hypothesis that two biologically distinct populations of insulin -expressing cells arise during pancreas formation.