Response of the exocrine pancreas to graded doses of secretin in calcium-treated and normal dogs.

Persisting modifications induced by repeated intravenous calcium infusion (acute hypercalcaemia) were investigated in 6 Thomas fistula dogs: 4 controls and 4 calcium-treated dogs, two of which were studied as controls. (a) The pancreatic response to graded doses of synthetic secretin (water and bicarbonate outputs) was significantly reduced in calcium-treated dogs when compared with controls. As both the D50 for secretin-induced response increased, and the maximal secretory response decreased, if may be concluded that calcium treatment decreased the sensitivity of duct cells to secretin and reduced their secretory capacity. (b) A similar dose-response relationship was observed between secretin and pancreatic calcium outputs in controls and calcium-treated dogs. The secretin induced pancreatic calcium secretion was independent of protein secretion and latter not being modified by secretin. Thus it may be assumed that the secretory fluid calcium originated form a protein independent pool and had a dose-dependent relationship to secretin. (c) These results help to illuminate the aetiology of chronic pancreatitis induced by acute hypercalcaemia and by hyperparathyroidism.