Amylase secretion by the perfused cat pancreas in relation to the secretion of calcium and other electrolytes and as influenced by the external ionic environment.

1. Amylase secretion from the perfused pancreas consists of two components: a small continuous basal secretion and a stimulated secretion in response to acetylcholine or cholecystokinin-pancreozymin. The response to small doses of either stimulant was repeatable over several hours.2. The calcium concentration of pancreatic juice, always less than that of the perfusate, was normally constant above secretory rates of 0.15 g/10 min. However, when the concentration of enzymes in the juice rose, either after stimulation or at very low secretory rates, the calcium concentration rose in parallel, suggesting that this calcium is bound to, or is a component of, pancreatic enzymes.3. Elevation of the perfusate calcium concentration resulted in a parallel increase in the calcium concentration of the pancreatic juice.4. Calcium-free solutions initially caused a small reduction in basal and stimulated amylase secretion and, after prolonged periods of perfusion, abolished stimulated secretion and caused a reduction in electrolyte secretion. The latter was completely reversed by calcium-rich perfusates but the effects on enzyme secretion were only partially reversible.5. Calcium-rich perfusates had no effect on the rate of electrolyte secretion but potentiated submaximally stimulated amylase secretion.6. Barium did not substitute for calcium in supporting pancreatic secretion.7. Alterations in the extracellular concentrations of sodium, potassium and magnesium had no direct effect on amylase secretion.8. The local anaesthetic tetracaine inhibited amylase secretion at a lower concentration than that required to inhibit electrolyte secretion.9. It is concluded (a) that calcium is secreted into the pancreatic juice in two fractions, one associated with enzymes and the other with the electrolyte component of the juice; and (b) that calcium ions play an important role in the stimulus-secretion coupling of pancreatic acinar cells, but that the effects of calcium depletion on electrolyte secretion may principally be due to alterations in the permeability of the duct system.