PANCREATIC INSULO-ACINAR PORTAL SYSTEMS IN HUMANS, RATS, AND SOME OTHER MAMMALS - SCANNING ELECTRON-MICROSCOPY OF VASCULAR CASTS

Scanning electron microscopy of vascular casts showed that in the mous e, rat, and guinea pig, the pancreatic endocrine islets were frequentl y interlobular in position and emitted insulo-venous efferent vessels directly draining into veins. In these animals, the intralobular islet s, located within the exocrine lobules, issued insulo-acinar portal ve ssels continuous with the lobular capillaries in addition to the insul o-venous efferent, vessels. In humans, monkeys, cows, pigs, dogs, cats , and rabbits, essentially all islets in the pancreas were intralobula r in location and emitted the insulo-acinar portal vessels only. In ma n and animals examined, especially in the murine species, many lobules lacked an islet, therefore the insular control over the exocrine panc reas seemed to be effected in more or less restricted areas of lobules . (C) 1997 Wiley-Liss, Inc.