Interaction of the tyrosine phosphatase inhibitor ortho-vanadate on stimulus--secretion coupling in pancreatic acinar cells.

Background: The effect of the tyrosine phosphatase inhibitor ortho-vanadate on stimulus-secretion coupling was investigated in isolated rat pancreatic acini.

Methods And Results: Ortho-vanadate (10(3)M) reduced cholecystokinin (CCK)-8 (10(10) M)-stimulated amylase release by 40% (IC50 = 5 x 10(4) M). In contrast, preincubation with 10(3) M ortho-vanadate increased secretin (5 x 10(9) M) and vasoactive intestinal peptide (VIP) (10(7) M)-induced amylase release by 65% and 80% (IC50= 3 x 10(-4) M), respectively.

Differential inhibitory effects of serine/threonine phosphatase inhibitors and a calmodulin antagonist on phosphoinositol/calcium- and cyclic adenosine monophosphate-mediated pancreatic amylase secretion.

Background: Protein phosphorylation and dephosphorylation events are considered to be key steps in the control of agonist-induced pancreatic enzyme release. This study was designed to characterize the role of serine/threonine phosphatases in phosphoinositol/calcium- and cyclic adenosine monophosphate (cAMP)-mediated stimulus-secretion coupling in rat pancreatic acini.

Methods: Isolated rat pancreatic acini were incubated with either the serine/threonine phosphatase inhibitors okadaic acid, calyculin A, and cyclosporin A or the calmodulin antagonist W-7.

Calyculin A, okadaic acid and W-7 interfere with a distal step in pancreatic acinar signal transduction.

The effects of the serine/threonine phosphatase inhibitors calyculin A, okadaic acid and the calmodulin antagonist W-7 on amylase secretion were studied in pancreatic acini. Calyculin A and okadaic acid dose-dependently inhibited amylase secretion to basal levels when stimulated with the intracellularly acting secretagogues thapsigargin, 8-br-cAMP or PMA. W-7 dose-dependently inhibited thapsigargin- or 8-br-cAMP-induced amylase secretion.

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.

Energy expenditure and substrate metabolism after oral fructose in patients with cirrhosis.

There is little information on the metabolic response to ingested fructose in patients with cirrhosis. Glucose kinetics, plasma lipid and blood lactate levels, whole body substrate oxidation rates and energy expenditure were measured following ingestion of 75 g fructose, in 8 cirrhotic patients and 6 controls. Fasting plasma glucose levels and rates of glucose appearance (Ra) and disappearance (Rd) were similar.