Acetylcholine-like effects of intracellular calcium application in pancreatic acinar cells

Iwatsuki, Naofumi; Petersen, O. H.

doi:10.1038/268147a0

Cited by 87 publications

(47 citation statements)

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“…It has previously been shown that certain divalent cations (Mn2+, Ni2+, Co2+), generally known to block transmembrane Ca2+ movement, interfere with the ACh-evoked uncoupling and from such studies it was concluded that the ACh-evoked uncoupling of pancreatic acinar cells was caused by an increase in [Ca2+]j (Iwatsuki & Petersen, 1978a). Intracellular Ca2+ injection mimics both membrane effects of ACh (surface membrane conductance increase and junctional membrane conductance decrease, Iwatsuki & Petersen, 1977;Petersen & Iwatsuki, 1978). It therefore appears that ACh primarily acts on Ca2+ translocation resulting in an increase in [Ca2+]i. Ca2+ acts on the surface membrane to increase its conductance (Petersen & Iwatsuki, 1978) and causes a decrease in pHi (Meech & Thomas, 1977) probably due to the mitochondrial Ca2+/H+ exchange (Lehninger, Reynafarje, Vercesi & Tew, 1978).…”

Section: Discussionmentioning

confidence: 99%

“…In high concentrations, these secretagogues almost abolish electrical intercellular communication. Even such total uncoupling is rapidly reversible (Iwatsuki & Petersen, 1977. In general, intercellular communication is thought to be controlled by variations in [Ca2+],, an increase in [Ca2+]i increasing the resistance of the junctional communication pathway (Loewenstein & Rose, 1978).…”

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confidence: 99%

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Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication

Iwatsuki

Petersen

1979

The Journal of Physiology

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SUMMARY1. Segments of mouse pancreatic or exorbital lacrimal gland were superfused with saline solutions. Under visual control two micro-electrodes were inserted into neighbouring cells within the same acinus or into neighbouring acini. Cell to cell electrical coupling was assessed by injecting rectangular current pulses through one electrode and measuring the electrotonic potential change in the same cell (V1) and in the neighbouring cell (V2). Acetylcholine (ACh) was added locally to impaled acini by micro-ionophoresis from an extracellular micropipette.2. Exposure of the tissues to a Krebs solution equilibrated with 100 % C02 caused a rapid increase in the size of electrotonic potential changes in the current injection cell and disappearance of the electrotonic potential changes in a neighbouring acinus or cell. This electrical uncoupling of previously coupled cells was rapidly reversible upon return to a solution equilibrated with 95 % 02 and 5 % CO2.3. Reduction of electrical intercellular coupling was also obtained using smaller C02 concentrations (50, 20 or 10 %). In these cases the effects developed more slowly and were less dramatic. Reducing the extracellular HCO3 concentration enhanced the uncoupling effect of 10 or 20 % C02. However, weak uncoupling effects were still observed using 10 or 20 % C02 in combination with a high bicarbonate concentration maintaining a constant extracellular pH (7.4).4. Reductions in extracellular pH (down to 5.5) achieved by varying combinations of Tris base and Tris HC1 had no effect on electrical coupling. Brief periods of anoxia (100 % N2) also had no effect.5. Exposure to 20 % C02 markedly enhanced the uncoupling effect of a brief ionophoretic pulse of ACh.6. Exposure of the tissue to 10 mM-NH4Cl, a procedure expected to increase the intracellular pH, counteracted the uncoupling effect of ACh. During sustained uncoupling caused by a sustained ACh stimulation a brief period of exposure to NH4C1 caused an immediate and fully reversible recoupling.7. It is concluded that variations in intracellular pH have marked effects on the electrical coupling between neighbouring cells in the pancreatic and lacrimal acinar tissue.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication

Iwatsuki

Petersen

1979

The Journal of Physiology

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“…High extracellular K depolarizes the acinar cell membrane without changing the membrane resistance (8) whereas ACh, CCK, gastrin, pentagastrin, caerulein, and bombesin all evoke a marked reduction in acinar cell surface membrane resistance (8)(9)(10). Stimulating pancreatic amylase secretion by raising the cytosol-ionized calcium concentration without receptor activation, with the divalent cation ionophore A23187 or direct intracellular Ca2+ injection, also causes membrane resistance reduction and depolarization (21,22).…”

Section: Discussionmentioning

confidence: 99%

In vitro action of bombesin on amylase secretion, membrane potential, and membrane resistance in rat and mouse pancreatic acinar cells. A comparison with other secretagogues.

Iwatsuki¹,

Petersen²

1978

J. Clin. Invest.

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“…The depolarization is thus unlikely to result from a failure of the membrane-electrode seal . A second possibility is that raising Ca" causes sufficient Ca" entry to reduce coupling between cells (De Mello, 1975 ;Iwatsuki and Petersen, 1977 ;Rose and Loewenstein, 1975). This could lead to depolarization of the impaled cell by the shunt resistance around the electrode, when the impaled cell is no longer supported by its neighbors.…”

Section: Possible Origins Of the Depolarization Induced By Divalent Cmentioning

confidence: 99%

“…This could lead to depolarization of the impaled cell by the shunt resistance around the electrode, when the impaled cell is no longer supported by its neighbors. This possibility can be discarded on the grounds that Mg", which is normally present in the cell at high concentration and does not cause uncoupling (De Mello, 1975 ;Iwatsuki and Petersen, 1977), has an effect on membrane potential similar to Ca". Transition elements also depolarize parathyroid cells, although they are very impermeant and do not directly affect cell coupling .…”

Section: Possible Origins Of the Depolarization Induced By Divalent Cmentioning

confidence: 99%

Depolarizing response of rat parathyroid cells to divalent cations.

López‐Barneo¹,

Armstrong²

1983

The Journal of General Physiology

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Membrane potentials were recorded from rat parathyroid glands continuously perfused in vitro. At 1 .5 mM external Ca", the resting potential averages -73 ± 5 mV (mean ± SD, n = 66). On exposure to 2.5 mM Ca", the cells depolarize reversibly to a potential of -34 ± 8 mV (mean ± SD). Depolarization to this value is complete in^-2-4 min, and repolarization on return to 1 .5 mM Ca" takes about the same time . The depolarizing action of high Ca" is mimicked by all divalent cations tested, with the following order of effectiveness: Ca" > Sr" > Mg" > Ba++ for alkali-earth metals, and Ca" > Cd++ > Mn++ > Co' > Zn ++ for transition metals . Input resistance in 1 .5 mM Ca" was 24 .35 ± 14 MQ (mean ± SD) and increased by an average factor of 2.43 ± 0 .8 after switching to 2.5 mM Ca++ . The low value of input resistance suggests that cells are coupled by low-resistance junctions. The resting potential in low Ca' is quite insensitive to removal of external Na+ or Cl -, but very sensitive to changes in external K+ . Cells depolarize by 61 mV for a 10=fold increase in external K+ . In high Ca+ +, membrane potential is less sensitive to an increase in external K+ and is unchanged by increasing K+ from 5 to 25 mM . Depolarization evoked by high Ca' may be slowed, but is unchanged in amplitude by removal of external Na+ or Cl-. Organic (13600) and inorganic (Co++, Cd++ , and Mn++) blockers of the Ca' channels do not interfere with the electrical response to Ca" changes. Our results show remarkable parallels to previous observations on the control of parathormone (PTH) release by Ca". They suggest an association between membrane voltage and secretion that is very unusual: parathyroid cells secrete when fully polarized, and secrete less when depolarized. The extraordinary sensitivity of parathyroid cells to divalent cations leads us to hypothesize the existence in their membranes of a divalent cation receptor that controls membrane permeability (possibly to K+) and PTH secretion .

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Acetylcholine-like effects of intracellular calcium application in pancreatic acinar cells

Cited by 87 publications

References 10 publications

Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication

Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication

In vitro action of bombesin on amylase secretion, membrane potential, and membrane resistance in rat and mouse pancreatic acinar cells. A comparison with other secretagogues.

Depolarizing response of rat parathyroid cells to divalent cations.

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