Calcium ion uptake in isolated pancreas cells induced by secretagogues.

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+.