This study evaluated the effect on an intravenous infusion of calcium chloride (4 and 8 mg/kg/hr) on both fasting and meal-stimulated pancreatic polypeptide (PP) release in an awake canine model. Intravenous calcium had no effect on fasting levels of PP. A protein-rich meal was a potent stimulus for PP release with a peak response of 1474 ± 266 pg/ml occurring at 45 min after the meal. Intravenous calcium at a dose of 8 mg/kg/hr augmented meal-stimulated PP release from 30 to 180 min after the meal compared to control values. Significant increases in serum calcium occurred at 60 to 180 min during infusion of calcium at 8 mg/kg/hr. This study demonstrates that the early cephalic (vagal) phase of pancreatic polypeptide release appears to be sensitive to subthreshold increases in extracellular calcium, suggesting that calcium is a factor in the stimulus-secretion coupling for the endogenous release of pancreatic polypeptide.
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