Serine/threonine phosphatases play a role in stimulus-secretion coupling in pancreatic acinar cells.
The role of serine/threonine phosphatases in Ca2+/IP3- and cAMP- mediated stimulus-secretion coupling was investigated in isolated pancreatic acinar cells. Cyclosporine A, an inhibitor of type 2b serine/threonine phosphatases, maximally reduced CCK-8-stimulated amylase secretion by 33%. In contrast, the secretory response to secretin or PACAP-(1-27) was not significantly altered by cyclosporine A independent of the secretagogue-concentration okadaic acid significantly reduced amylase release, induced by Ca2+/IP3-mediated- (CCK-8) or cAMP-mediated agonists (secretin, PACAP-(1-27), VIP) at concentrations that primarily inactivate type 1 and 2b phosphatases. Calyculin A, another type 1 and 2a phosphatase inhibitor, had a similar inhibitory effect on CCK-8-, secretin- or PACAP-(1-27)-induced secretion. In permeabilized acini, cyclosporine A reduced calcium-induced amylase release by 20%, whereas okadaic acid and calyculin A had an inhibitory effect by 55% and 52%, respectively. The ultrastructure of CsA-incubated acinar cells was not different from vehicle-incubated control lobules. In contrast, incubation with okadaic acid for 60 min resulted in morphological alterations of the Golgi apparatus, leading to a fragmentation of Golgi cisternae into small vesicles. Our data suggest a role of type 1 and 2b phospatases in stimulus-secretion coupling of both signal-transduction pathways in pancreatic acinar cells. These phosphatases might also be important for the maintenance of pancreatic cellular ultrastructure.
Schmidt
W E
WE
Labor für Molekulare Gastroenterologie, Christian-Albrechts-Universität Kiel.
Meyer-Alber
A
A
Waschulewski
I H
IH
Fetz
I
I
Höcker
M
M
Kern
H F
HF
Fölsch
U R
UR
D000681:Amylases / Q000378:metabolism*; D000818:Animals; D046508:Culture Techniques; D016572:Cyclosporine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004988:Ethers, Cyclic / Q000494:pharmacology; D008297:Male; D008387:Marine Toxins; D008854:Microscopy, Electron; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology; D010179:Pancreas / Q000187:drug effects / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012636:Secretory Rate / Q000187:drug effects; D015398:Signal Transduction / Q000502:physiology*; D013912:Threonine / Q000037:antagonists & inhibitors / Q000502:physiology*
D004988:Ethers, Cyclic; D008387:Marine Toxins; D010080:Oxazoles; D019319:Okadaic Acid; D013912:Threonine; C059041:calyculin A; D016572:Cyclosporine; D010749:Phosphoprotein Phosphatases; D000681:Amylases