Novel tool for the study of cholecystokinin-stimulated pancreatic enzyme secretion.

Abstract

The molecular events that mediate cholecystokinin (CCK)-

Study of the states and populations of the rat pancreatic cholecystokinin receptor using the full peptide antagonist JMV 179

“…This result confirms previous reports [8] and suggests a more complex activation process and/or signal transduction pathway as recently documented [31].…”

Supramaximal cholecystokinin displaces Munc18c from the pancreatic acinar basal surface, redirecting apical exocytosis to the basal membrane

“…It is well established that CCK-8 dose-dependently stimulates secretion of amylase from dispersed rat pancreatic acini, which reaches maximal secretion at 100 pM, and at supramaximal concentrations (i.e., 10 nM CCK-8) an inhibition of secretion from the maximal level is observed (3,8). In contrast to CCK, CCK-OPE is as efficacious a secretagogue but does not exhibit an inhibition of secretion at supramaximal doses (>0.1 µM) (8). We examined acini exposed to these CCK-8 stimulation protocols for the locations of Munc18c, syntaxin-4, and SNAP-23 by laser confocal microscopy.…”

“…The preparation of isolated rat acini was performed by a mechanical and enzymatic dissociation technique as we have previously described (8)(9)(10)(11). The acini were resuspended in oxygenated Krebs-Ringer-HEPES buffer, consisting of (in mM): 104 NaCl, 5 KCl, 1 KH 2 PO 4 , 1.2 MgCl 2 , 2 CaCl 2 , 0.2% (wt/vol) BSA, 0.01% (wt/vol) soybean trypsin inhibitor, 10 mM glucose, 25 mM HEPES/NaOH, pH 7.4, supplemented with MEM and glutamine.…”

“…Regulated apical exocytosis in pancreatic acinar cells is very efficiently effected by physiologic CCK (or CCK-OPE) concentrations (3,8) despite the limited surface area of the apical plasma membrane. Homotypic fusion mechanisms would be an efficient means to rapidly deliver large quantities of ZG contents into the duct, since the large granules would not need to be moved toward and make contact with the apical plasma membrane but could fuse with adjacent granules.…”

The peripheral cholecystokinin receptors

“…As regards receptor activation by JMV-180, although it has been observed that JMV-180 binding is insensitive to GTP [182] and that JMV-180 does not seem to promote activation of guanine-nucleotide-binding regulatory protein(s) on plasma membranes [177], other studies have documented the interaction of JMV-180 with two affinity classes of sites on rat /166, 1681 and mouse 11671 pancreatic acini. In addition, a recent study on digitonin-permeabilized acini has suggested the involvement of guanine-nucleotide-binding regulatory protein in JMV-180-stimulated secretion [ 181 1.…”