Nonparallel secretion of GP-2 from exocrine pancreas implies luminal coupling between acinar and duct cells

Am J Physiol. 1994 Jul;267(1 Pt 1):G40-51. doi: 10.1152/ajpgi.1994.267.1.G40.

Abstract

The in vivo and in vitro secretion of glycoprotein-2 (GP-2), a glycosyl phosphatidylinositol (GPI)-anchored protein from the rat exocrine pancreas, was characterized. GP-2 was secreted in a nonparallel manner compared with amylase, a marker of secretory enzymes. Attenuated GP-2 secretion correlated with hormones that stimulated exocytosis in acinar cells. Augmented GP-2 secretion correlated with hormones that stimulated fluid and bicarbonate secretion from ductal elements. Immunofluorescence studies identified an enriched pool of GP-2 tightly bound to the apical membranes of acinar cells in addition to zymogen granules. This non-zymogen granule pool appears to represent the source of GP-2 released from acinar cells in a nonparallel manner. With the use of dispersed pancreatic acini largely devoid of ductal elements, GP-2 release was found to be augmented by alkaline pH. Thus GP-2 secretion appears to be modulated by two discrete cellular processes: 1) delivery of prereleased GP-2 within zymogen granules to the ductal lumen by exocytic mechanisms and 2) enzymatic release of GPI-anchored GP-2 from the luminal membranes, a kinetic process that appears to be regulated by secretin- or carbachol-induced secretion of bicarbonate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amylases / metabolism
  • Animals
  • Bicarbonates / pharmacology
  • Cell Communication
  • Fluorescent Antibody Technique
  • Glycosylphosphatidylinositols / metabolism
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Male
  • Membrane Glycoproteins / metabolism*
  • Pancreas / cytology
  • Pancreas / metabolism*
  • Rats
  • Rats, Wistar

Substances

  • Bicarbonates
  • Glycosylphosphatidylinositols
  • Membrane Glycoproteins
  • glycoprotein-2, pancreas
  • Amylases