Stimulus‐secretion coupling in pancreatic acinar cells: influences of external sodium and calcium on responses to cholecystokinin‐pancreozymin and ionophore A23187
Open Access
- 1 August 1977
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 270 (1), 9-28
- https://doi.org/10.1113/jphysiol.1977.sp011935
Abstract
1. The roles of Na and Ca ions in stimulus‐secretion coupling were analysed in the isolated and perfused rat pancreas. 2. Partial replacement of NaCl with LiCl produced a diminution in both amylase output and pancreatic juice flow which were induced by 5 m‐u. CCK‐PZ/ml., and almost normal responses were usually regained immediately after the reintroduction of a standard concentration of NaCl. Nearly total replacement of NaCl with LiCl caused an almost complete inhibition of the responses, although 25 m M‐NaHCO3 and 1 m M‐NaH2PO4 were still present, and only partial recovery was obtained after the re‐introduction of a standard concentration of NaCl. 3. A quantitative relationship was found between the amount of amylase released by CCK‐PZ and the [Na+]o over the range 26‐157 m M in the presence of 2·5 m M‐Ca. A similar relationship was also observed when [Ca2+]o was decreased to 1·0 m M, but the responses were reduced to about one half of those observed with 2·5 m M‐Ca. 4. The most satisfactory theory which explains the cellular mechanism of CCK‐PZ‐induced amylase output, and which fits the experimental data, requires the dominant activity of a complex composed of a carrier molecule bearing one Ca and four Na molecules, if there is no interaction between Na+ and Li+. 5. A quantitative relationship was also found between the amount of pancreatic juice flow stimulated by CCK‐PZ and [Na+]o, over the range 26‐157 m M, in the presence of 1·0 or 2·5 m M‐Ca. 6. A similar quantitative relationship was found between the amount of amylase released by Ca‐ionophore A23187 and [Na+]o in the presence of 2·5 or 5·0 m M‐Ca. The most satisfactory theory which fits this experimental data also requires the dominant activity of a complex composed of a carrier molecule bearing one Ca and four Na molecules, if there is no interaction between Na+ and Li+.This publication has 34 references indexed in Scilit:
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