[Calcium homeostasis and exocrine pancreas: physiological ans pathological interrelations]

Calcium homeostasis and exocrine pancreas interact on several levels under both physiologic and pathophysiologic conditions. (1) Calcium ions are important intracellular mediators of cholinergic and hormonal stimulation of the pancreatic acinar cell, and thus play a central role in the stimulus-secretion coupling of ecbolic pancreatic function. (2) The calcium concentration in pancreatic juice is lower than in the interstitial fluid: pancreatic juice calcium is composed of two fractions, one of which is secreted together with enzyme proteins and the other diffuses along paracellular pathways dependent on serum calcium. Disturbed calcium secretion in pancreatic juice can be observed even following slight pancreatic alteration; conversely, disturbed calcium secretion may be of importance in the pathogenesis of chronic calcifying pancreatitis. (3) Hypocalcemia is an important symptom of acute pancreatitis whose pathogenesis has not been fully elucidated. (4) On the other hand, pancreatitis complicates chronic and acute hypercalcemic syndromes though the pathogenic mechanisms is uncertain. Experimental chronic hypercalcemia in animal models causes characteristic pancreatic secretory changes and disturbs the diffusion barrier for calcium. Experimental acute hypercalcemia causes stimulation of pancreatic enzyme secretion and cholecystokinin release. In addition, extracellular calcium has a direct stimulatory effect on pancreatic acinar cells in vitro.