Effect of divalent cations on gastrointestinal hormone release and exocrine pancreatic secretion in dogs

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Abstract
The effect of 3 common divalent cations (Ca2+, Mg2+ and Zn2+) on the release of cholecystokinin (CCK-33), pancreatic polypeptide (PP) and gastric was examined. Five dogs with pancreatic and gastric fistulas were given 1-h intraduodenal infusions of Ca (5 mmol .cntdot. kg-1 .cntdot. h-1), Mg (4 mmol .cntdot. kg-1 .cntdot. h-1), or Zn (1 mmol .cntdot. kg-1 h-1). At another time the same dogs were given an i.v. bolus followed immediately by a 1-h infusion of Ca (0.36 mmol/kg [bolus], 0.36 mmol .cntdot. kg-1 .cntdot. h-1), Mg (0.25 mmol/kg [bolus], 0.25 mmol .cntdot. kg-1 .cntdot. h-1), or Zn (0.03 mmol/kg [bolus], 0.03 mmol .cntdot. kg-1 .cntdot. h-1). Intraduodenal infusions of Ca, Mg and Zn significanly stimulated CCK-33, PP, and gastrin release. I.v. Ca stimulated CCK-33, PP and gastrin release to 245, 193 and 155% of basal levels, respectively. I.v. Mg increased CCK-33 to 123% of basal levels but did not stimulate PP and gastrin levels. I.v. Zn stimulated release of CCK-33, PP and gastrin to 126, 185 and 124%, respectively. Ca, Mg and Zn can stimulate release of CCK-33, PP and gastrin in much the same manner. These cations may have a nonspecific electrical action that results in an alteration of membrane permeability, which leads to release gastrointestinal hormones.