Abstract
The thymidine analog, 5-bromodeoxyuridine (BrdU), inhibits the differentiation of the acinar cells of the embryonic rat pancreas, while having little effect on the growth of the tissue. The BrdU-treated pancreas contains elevated alkaline phosphatase and carbonic anhydrase activities, and, unlike the normal pancreas, contains numerous extracellular fluid-filled vacuoles, surrounded by ductlike cells. Both alkaline phosphatase and carbonic anhydrase activities are located preferentially in the ductlike cells lining the vacuoles. The biochemical, morphological, and functional features of these epithelial cells are therefore characteristic of the normal pancreatic duct cell. Thus, in the exocrine pancreas, BrdU seems to alter the normal program of differentiation by favoring the functional duct cells while inhibiting the differentiation of acinar cells.