Interactions of calcium, magnesium and atropine on exocrine pancreatic secretion in man

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.

Dose-dependent, and long-lasting, effects of repeated intravenous injections of calcium on the canine secretin-stimulated pancreatic juice secretion

The effects of repeated intravenous calcium administration on pancreatic juice secretion were investigated in four Thomas fistula dogs. During stimulation by 1.0 U kg-1h-1 GIH secretin, three Ca doses were administered: 2, 4 and 8 mu mol kg-1 min-1 during 1 h, saline being used in control tests; one dose only was tested per day. It was found that Ca administration induced both acute and long-lasting effects. Acute effects were characterized by an increased response to secretin stimulation. Fluid, HCO3(-), protein and Ca outputs increased significantly in a dose-dependent manner, the increase of protein output being the most dramatic. Long-lasting effects, until now unrecognized, were characterized by a progressive increase of protein secretion during the first hour of secretin stimulation. This increase kept going during the 3 months of repeated calcium injections. Although protein plugs were observed in the juice, sometimes stopping the flow of juice, no pancreatic lesion was found. A second protocol showed that, after discontinuing calcium injections, the long-lasting effects decreased progressively, but protein hypersecretion was still significant 3.5 months later. The importance of these findings regarding chronic pancreatitis due to hyperparathyroidism is discussed.