The role of extracellular Ca2+ and cyclic nucleotides in the mechanism of enzyme secretion from the cat pancereas

Schulz, Irene; Mannigel, H.; Christian, Anna‐Luise; Wiechmann, Jutta

doi:10.1007/bf00580539

Cited by 33 publications

(13 citation statements)

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“…It is the general hypothesis that secretagogue-induced rise of cytosolic free Ca 2 § concentration triggers enzyme release from pancreatic cells [16,22,31,35,36,52,56,58,65]. Experiments in which isolated acinar cells had been preincubated with 45Ca2 § until steady state had been reached have shown biphasic ~SCa 2 + movements following stimulation with secretagogues of en-zyme secretion.…”

Section: Introductionmentioning

confidence: 99%

Calcium uptake into acini from rat pancreas: Evidence for intracellular ATP-dependent calcium sequestration

et al. 1982

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Intracellular ATP-dependent Ca2+-sequestration mechanisms were studied in isolated dispersed rat pancreatic acini following treatment with saponin or digitonin to disrupt their plasma membranes. In the presence of 45Ca2+ concentrations less than 10(-6) mol/liter, addition of 5 mmol/liter ATP caused a rapid increase in 45Ca2+ uptake exceeding the control by fivefold. ADP mimicked the ATP effect by 50 to 60%, whereas other nucleotides such as AMP-PNP, AMP-PCP, CTP, UTP, ITP, GTP, cAMP and cGMP did not. Maximal ATP-promoted Ca2+ uptake was obtained at 10(-5) mol/liter Ca2+. Inhibition of Ca2+ uptake by mitochondrial inhibitors was dependent on the Ca2+ concentration, indicating the presence of different Ca2+ storage systems. Whereas the apparent half-saturation constant found for mitochondrial Ca2+ uptake was approximately 4.5 X 10(-7) mol/liter, in the presence of antimycin and oligomycin (nonmitochondrial uptake) it was approximately 1.4 X 10(-8) mol/liter. In the absence of Mg2+ both ATP- and ADP-promoted Ca2+ uptake was nearly abolished. The Ca2+ ionophore and mersalyl blocked Ca2+ uptake, Electron microscopy showed electron-dense precipitates in the rough endoplasmic reticulum of saponin-treated cells in the presence of Ca2+, oxalate and ATP, which were absent in intact cells and in saponin-cells without ATP or pretreated with A23187. The data suggest the presence of mitochondrial and nonmitochondrial ATP-dependent C2+ storage systems in pancreatic acini. The latter is likely to be located in the rough endoplasmic reticulum.

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Section: Introductionmentioning

confidence: 99%

Calcium uptake into acini from rat pancreas: Evidence for intracellular ATP-dependent calcium sequestration

et al. 1982

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“…[Ca2+], may be produced by an increase in the passive Ca-influx into the pancreatic acinar cells (Kanno, 1972;Dean & Matthews, 1972;Matthews, Petersen & Williams, 1973;Schulz, 1975; Kondo & Schulz, 1976 (Kanno, 1972;Kanno & Nishimura, 1976). It was also observed that replacement of [Na+]o by [Li+]o in the perfusion solution inhibited the CCK-PZ-induced amylase release in the isolated and perfused rat pancreas (Kanno, 1975 Kanno (1974Kanno ( , 1975 has proposed a working hypothesis which states that the activity of an electrogenic Na pump may maintain the increase in carrier-mediated Ca2+ influx.…”

Section: Introductionmentioning

confidence: 99%

Stimulus‐secretion coupling in pancreatic acinar cells: influences of external sodium and calcium on responses to cholecystokinin‐pancreozymin and ionophore A23187

Kanno¹,

Saito²,

Sato³

1977

The Journal of Physiology

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SUMMARY1. 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 mM-NaHCO3 and 1 mM-NaH2PO4 were still present, and only partial recovery was obtained after the reintroduction of a standard concentration of NaCl.

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“…High concentrations of extracellular Ca2+ have previously been shown to evoke enzyme secretion from the isolated pancreas of the cat (Schulz & Mannigel, 1974;Schulz, 1975) and mouse (Petersen & Ueda, 1976) but not the dog (Teufel, Stock, Rohrmoser & Forell, 1977 (Chapman & Ellis, 1977) and smooth muscle (Nonomura, Hotta & Ohashi, 1966;Collins, Sutter & Teiser, 1972), which both depend heavily on extracellular Ca2+ for excitation-contraction coupling, but has a much smaller effect in skeletal muscle (Chiarandini & Stephani, 1973;Langer, Serena & Nudd, 1975;Toda, 1976) which relies largely on intracellular Ca2+ stores in the sarcoplasmic reticulum.…”

Section: Methodsmentioning

confidence: 99%

The effects of manganese, cobalt and calcium on amylase secretion and calcium homeostasis in rat pancreas

Argent

Case

Hirst

1982

The Journal of Physiology

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SUMMARY1. Mn2+ evoked an atropine-resistant secretion of amylase from the isolated pancreas of the young rat. The lowest effective concentration of Mn2+ was 10-3 M. The response to 10-2 M-Mn2+ was biphasic, an initial peak being followed by a slow sustained rise in amylase output. The maximal effect of 10-2 M-Mn2+ was to double the basal rate of amylase secretion after 70 min incubation.2. Co2+ (10-2 M) also stimulated amylase secretion. The maximal rate, about three times the basal value, was attained after 20 min incubation. Atropine partially inhibited this effect.3. Ca2+ (10-2 M) evoked an atropine-resistant amylase secretion similar in both magnitude and time course to the sustained phase observed with 10-2 M-Mn2+.4. Mn2+ (10-4-10-2 M) also increased the rate of45Ca efflux from the gland. Maximal efflux rates were attained after 30 min incubation and thereafter declined to basal values. A small increase was also observed with 10-2 MCo2+, but not with 10-2 M-Ca2+. The effect of Co2+ was almost completely abolished by atropine.5. Reducing the extracellular Ca2+ concentration from 2-5 x 10-3 to 10-5 M did not reduce amylase secretion in response to 10-2 M-Mn2+, but secretion was abolished in a Ca2+-free medium containing EGTA. The increase in 45Ca efflux rate evoked by Mn2+ was inversely related to the extracellular Ca2+ concentration.6. Mn2+ (10-2 M) increased the concentration of cyclic 3',5'-guanosine monophosphate (cyclic GMP) within the pancreas. Also, Mn2+ accumulated within the cellular pool of the gland. The time course of both these effects was similar to the time course of 45Ca efflux. 10. When glands were exposed to ACh and Mn2+ simultaneously, the time required for inhibitory effects to develop was inversely related to the dose of ACh and the concentration of Mn2+.11. Mn2+ did not alter the acceleration of 45Ca efflux evoked by ACh or by caerulein in a medium containing 25 x 10-3 M-Ca2+. However, under conditions of Ca2+ deprivation ACh-stimulated 45Ca efflux was greatly enhanced.12. Mn2+ reduced the total amount of Ca2+ accumulated into the cellular pool of the pancreas after 60 min incubation, but had no effect on the initial, rapid phase of Ca2+ uptake.13. The effects of Mn2+ on the relationship between ACh dose, amylase release and the extracellular Ca2+ concentration suggest that the inhibitory actions of Mn2+ cannot be explained by a simple, competitive interaction with the stimulant or with extracellular Ca2+. However, the time course of inhibition is consistent with a requirement for Mn2+ to accumulate within the acinar cells.14. Mn2+ partially inhibited amylase secretion stimulated by hyperosmolarity and also increased the 45Ca efflux rate under these conditions. 15. Our results are not consistent with Mn2+ exerting its inhibitory effect on secretagogue-stimulated enzyme secretion solely by blocking Ca2+ influx from the extracellular space. We conclude that inhibition probably depends on the ability of Mn2+ to displace Ca2+ from binding sites involved in secretion, presumably coupled with ...

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The role of extracellular Ca2+ and cyclic nucleotides in the mechanism of enzyme secretion from the cat pancereas

Cited by 33 publications

References 34 publications

Calcium uptake into acini from rat pancreas: Evidence for intracellular ATP-dependent calcium sequestration

Calcium uptake into acini from rat pancreas: Evidence for intracellular ATP-dependent calcium sequestration

Stimulus‐secretion coupling in pancreatic acinar cells: influences of external sodium and calcium on responses to cholecystokinin‐pancreozymin and ionophore A23187

The effects of manganese, cobalt and calcium on amylase secretion and calcium homeostasis in rat pancreas

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