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Abstract

1. Secretagogues of pancreatic enzyme secretion: pancreozymin, carbamylcholine, gastrin I, the octapeptide of pancreozymin, caerulein and the Ca²⁺ ionophore A 23187 stimulate ⁴⁵Ca uptake into isolated rat pancreatic cells, whereas adrenaline, isoproterenol, secretin, dibutyrylic cyclic adenosine 3',5'-monophosphate and dibutyrylic cyclic guanosine 3',5'-monophosphate have no effect on ⁴⁵Ca uptake. 2. A graphical analysis of the Ca²⁺ uptake curves reveals at least two phases: a fast phase, probably due to binding of Ca²⁺ to the membrane and a slow phase representing Ca²⁺ transport into cells. Both phases are stimulated by pancreozymin and carbamylcholine. 3. The ⁴⁵Ca-exchangeable pool size is increased by both carbamylcholine and pancreozymin, whereas a significant increase of total content of cell calcium was too small to be detected. 4. Atropine blocks the stimulatory effect of carbamylcholine completely but not that of pancreozymin. The Ca²⁺ antagonist D600 blocks the stimulatory effects of both carbamylcholine and pancreozymin only partially. 5. The data suggest that secretagogues of pancreatic enzyme secretion act by increasing the rate of Ca²⁺ transfer into the cell most probably through an increase of the cell membrane permeability for Ca²⁺.