Calcium secretion from the feline pancreas. Influence of hormonal and cholinergic secretagogues and of serum calcium.

The influences of secretagogues and of elevated serum calcium concentrations on the calcium secretion from the cat pancreas have been studied in vivo. During a high and constant fluid secretion rate evoked by a background infusion of secretin, additional infusions of both cholecystokinin-pancreozymin and urecholine led to a dose-dependent increase in calcium secretion in pancreatic juice parallel to the rise of protein. The amount of calcium in pancreatic juice associated to 1 mg protein (18.3 nmol/mg protein) calculated from regression analysis was independent of dose or kind of stimulus used. The protein-independent pancreatic juice calcium fraction was 0.184 mM in normocalcemia. During an episode of hypercalcemia produced by an intravenous calcium infusion, the protein-independent calcium fraction was increased and correlated linearly to the serum calcium concentration. We conclude that pancreatic juice calcium consists of two major fractions, one being associated with the enzyme protein and stimulated by secretagogues, and the other being protein independent and directly dependent on the extracellular calcium concentration.