EFFECT OF ACETYLCHOLINE STIMULATION ON CALCIUM AND SODIUM UPTAKE BY THE ISOLATED RAT PANCREAS

1. The role of Ca2+ and Na+ ions in 'stimulus‐secretion' coupling in the isolated uncinate pancreas of 4‐week‐old rats has been examined using radioisotope tracer techniques. The amount of 45Ca2+ and 22Na+ (mumole/g wet wt.) taken up by unstimulated glands was compared to that of glands in which amylase release was stimulated by ACh(10(‐5) M) at various incubation times. 2. The amount of 45Ca taken up by the glands within 60 min of incubation was not found to be increased by the presence of ACh(10(‐5) M). In fact, during short incubation periods the 45Ca uptake was significantly less in the stimulated glands than the unstimulated glands. 3. Presence of ACh(10(‐5) M) did cause a significant initial increase in 22Na uptake lasting up to 20 min from onset of stimulation. 4. These results indicate that the rise in intracellular Ca2+ concentration which is suggested by an increase in 45Ca efflux during the action of pancreatic secretagogues, is not a consequence of increased 45Ca uptake by the pancreas; but they indicate that an initial action of ACh could be to elicit an increase in Na+ influx and that Na+ ions are likely to be involved in the action of ACh on pancreatic acinar cells. © 1979 The Physiological Society