|[Frontiers in Bioscience 2, d271-282, June 1, 1997]|
THE ROLE OF LANGERHANS ISLETS IN PANCREATIC DUCTAL ADENOCARCINOMA|
Parviz M. Pour
The UNMC/Eppley Cancer Center, University of Nebraska
Medical Center, Omaha, NE
Received 5/6/97 Accepted 6/2/97
Until the turn of this century, and probably based on the Pearce hypothesis on the neuroectodermal origin of islet cells, the endocrine pancreas was considered an independent part of the pancreas. In 1911 Bensley (24) showed that ductal/ductular structures penetrate through some islets in guinea pigs suggesting the existence of an intimate physiological and anatomical contact between the exocrine and endocrine tissues. The shape, size, and distribution of islets is rather uniform (25) in all species and is independent of the animal size. The recognition of a portal vascular system (see ref. 26) was another early step in recognizing the existence of an association between the exocrine and endocrine pancreas. Several independent researchers showed that at least part of the exocrine blood supply of pancreas is derived from the insular arteries that first pass through islets. This blood supply explained the remarkable "halo" phenomenon that is particularly accentuated in the rat pancreas. Using a hematoxylin-eosin stain, rat acinar cells in the vicinity of islets (periinsular) appear larger and have more eosinophilic zymogen granules than those remote from islets (teleinsular acinar cells) causing a "halo" around the faintly stained islets (26). This phenomenon was thought to be the result of a higher concentration of insulin (which has a promoting effect on cellular DNA and protein content) in the vessels passing through the periinsular acini than in the teleinsular region. This concept was supported by the later finding that destruction of islet b-cells by alloxan results in the disappearance of the halo phenomenon (27). Further support for the intimate interaction of the exocrine and endocrine pancreas was shown by the presence of hormones released by the islets of Langerhans in the pancreatic juice of several species, including humans (28).