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

Iwatsuki, Naofumi; Petersen, O. H.

doi:10.1113/jphysiol.1979.sp012815

Cited by 61 publications

(36 citation statements)

References 18 publications

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“…Separate experiments performed with the alkanols in the presence of 10-6-10 -5 M carbamylcholine also showed uncoupling of the acinar cells. However, this effect could not be unequivocally interpreted since at these concentrations, which elicit maximal amylase secretion, carbamylcholine alone could uncouple the cells of dispersed acini, as previously reported for several other pancreatic secretagogues (9,15,16,28). That the two alkanols tested did not perturb intercellular communication by damaging the cells was shown by the normal ultrastructure of the acini, their preserved maximal secretory response to carbamylcholine, and the rapid recovery of normal coupling and basal secretion after the acini were returned to control medium.…”

Section: Discussionmentioning

confidence: 81%

“…As expected (9,15,16,28), carbamylcholine rapidly depolarized and uncoupled at least partially the acinar cells.…”

Section: Dye Couplingmentioning

confidence: 77%

“…Since uncoupling did not either result from the disappearance of gap junctions, it is likely that heptanol and octanol decreased the permeability of existing junctional channels. Cytosolic free calcium and c3'tosolic pH are considered the most likely mediators of junctional permeability in most tissues (13,20,34), including the pancreatic acinar cells (15,16,29). However, fluorescence measurements from acini loaded with either quin2 or 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein revealed no effect of the alkanols on either one of these two factors, indicating that they were probably not involved in the uncoupling mechanism.…”

Section: Discussionmentioning

confidence: 98%

“…The observation that dispersed acinar cells do not respond to secretagogues as isolated acini (1,12,27,38) led to suggest that direct interactions between neighboring cells may play a role in the normal functioning of the pancreatic acinus. The additional finding that several secretagogues uncouple the cells of pancreatic acini at concentrations that elicit maximal enzyme secretion (9,15,16,28) further suggested that if junctional coupling is related to the secretory activity of acinar cells (28)(29)(30), it is probably not obligatory for their acute maximal secretory response. As yet, however, the possible relationship between acinar cell-to-cell coupling and enzyme secretion has not been investigated.…”

mentioning

confidence: 99%

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Blockage of cell-to-cell communication within pancreatic acini is associated with increased basal release of amylase.

Meda¹,

Bruzzone²,

Knodel³

et al. 1986

The Journal of Cell Biology

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Abstract. To assess whether junctional coupling is involved in the secretory activity of pancreatic acinar cells, dispersed rat acini were incubated for 30 min in the presence of either heptanol (3.5 mM) or octanol (1.0 mM). Exposure to either alkanol caused a marked uncoupling of the acinar cells which, in control acini, were extensively coupled. Uncoupling was associated with an increased basal release of amylase that was at least twice that of controls. By contrast, carbamylcholine (10 -5 M)-induced maximal amylase secretion, cytosolic pH, and free Ca 2÷, as well as the structure of gap junctions joining the acinar cells, were unaffected. Both uncoupling and the alteration of basal secretion were already observed after only 5 rain of exposure to heptanol, they both persisted throughout the 30-rain exposure to the alkanols, and were reversible after removal of either heptanol or octanol. Since neither of the two uncouplers appeared to alter unspecifically the secretory machinery and the nonjunctional membrane of acinar cells, the data are consistent with the view that junctional coupling participates in the control of the basal secretion of acinar cells.AP junctions (11) and coupling (10, 17, 31) have been described for a long time between the acinar cells of the exocrine pancreas, but their function in these cells is still undetermined, as is the case in most other electrically inexcitable adult tissues (13, 20). The observation that dispersed acinar cells do not respond to secretagogues as isolated acini (1,12,27,38) led to suggest that direct interactions between neighboring cells may play a role in the normal functioning of the pancreatic acinus. The additional finding that several secretagogues uncouple the cells of pancreatic acini at concentrations that elicit maximal enzyme secretion (9, 15,16,28) further suggested that if junctional coupling is related to the secretory activity of acinar cells (28-30), it is probably not obligatory for their acute maximal secretory response. As yet, however, the possible relationship between acinar cell-to-cell coupling and enzyme secretion has not been investigated. To approach this question, we have studied whether a short period of reversible uncoupling affects amylase secretion from dispersed rat acini.Among the methods available to induce uncoupling, those that affect cytosolic free Ca 2+ ([Ca2+]i),l cytosolic pH (pHi), or ATP (20, 34) are not appropriate for this study since these factors are also involved in the control of secretion and, thus, make it impossible to establish whether secretory changes are specifically related to uncoupling. Antibodies directed against gap junctions appear as ideal tools to address this question. Unfortunately, the antibodies so far available are active only -1. Abbreviations used in this paper: [Ca2+], cytosolic free Ca2+; control KRB, Krebs-Ringer-bicarbonate medium containing 12.5 mM Hepes and 0.1% serum albumin; pH,, cytosolic pH. upon intracellular application (14,18,36) and presently cannot be incorporated into the relative...

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Section: Discussionmentioning

confidence: 81%

“…As expected (9,15,16,28), carbamylcholine rapidly depolarized and uncoupled at least partially the acinar cells.…”

Section: Dye Couplingmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 99%

See 2 more Smart Citations

Blockage of cell-to-cell communication within pancreatic acini is associated with increased basal release of amylase.

Meda¹,

Bruzzone²,

Knodel³

et al. 1986

The Journal of Cell Biology

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“…abolished coupling within 20 s in fish blastomeres (5), 1 min in mouse pancreas acinar cells (15), and 2 .5 min in amphibian embryos (26); in all three instances, coupling could be restored on a time-scale of seconds or minutes. These discrepancies between structural and physiological events raise doubts that crystallization of the connexons represents the structural correlate of uncoupling.…”

Section: Rapid Communications Figures 8-10mentioning

confidence: 99%

Structure of rapidly frozen gap junctions.

Raviola¹,

Goodenough²,

Raviola³

1980

The Journal of Cell Biology

150

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The structure of gap junctions in the rabbit ciliary epithelium, corneal endothelium, and mouse stomach and liver was studied with the freeze-fracturing technique after rapid freezing to near 4°K from the living state . In the ciliary epithelium, the connexons were randomly distributed, separated by smooth membrane matrix . In the corneal endothelium, both random and crystalline arrangements of the connexons were observed . In the stomach and liver, the connexons were packed but not crystalline . Experimental anoxia or lowered pH caused crystallization of the connexons within 20-30 min . In the ciliary epithelium, the effects of prolonged anoxia or low pH could not be reversed . In addition, invaginated or annular gap junctions increased in number, but their connexons were usually distributed at random . Rapid freezing thus demonstrates that gap junctions of different tissues are highly pleiomorphic in the living state, and this may explain their variations in structure after chemical fixation . The slow time-course and irreversibility of the morphological changes induced by prolonged anoxia or low pH suggest that connexon crystallization may be a long-term consequence rather than the morphological correlate of the switch to high resistance .When gap junctions are chemically fixed and subsequently analyzed with the freeze-fracturing technique, the clustering of their subunits (particles or connexons) in the plane of the membrane varies in different tissues and often in different cells of the same tissue: hexagonal packing and complete randomness are the extreme configurations, but a great variety of intermediate arrangements have been described (4,10,20) . The functional correlate of these variations is not known, but it seems unlikely that they could reflect differences in the resistance state ofthe junctions. In fact, it was shown that aldehyde fixation abolishes coupling, and therefore freeze-fractured gap junctions in fixed tissues are probably visualized in their highresistance state (3) . Nevertheless, differences in the degree of clustering of the connexons were observed in tissues exposed to uncoupling agents before fixation as compared with their untreated controls (12, 21, 22); thus, it was proposed that the switch to high resistance is accompanied by movement of the connexons in the plane of the membrane and their lateral association in a compact, crystalline lattice . There are exceptions, however, to this behavior, because uncoupling agents did not seem to affect the state of connexon aggregation in the gap junctions of the lens (11).These observations raise important questions on the structure of gap junctions in vivo, and on the time-course of crystallization and its precise relationships with uncoupling. Such questions, however, can only be answered if the structure of gap junctions can be analyzed and experimentally manipulated in absence of chemical fixation. For this reason, we used the technique of rapid-freezing to near 4°K (14, 28) on a variety of tissues. With this method, freezing...

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Electrophysiology of Salivary and Pancreatic Acinar Cells

Maruyama

1989

Comprehensive Physiology

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

Cited by 61 publications

References 18 publications

Blockage of cell-to-cell communication within pancreatic acini is associated with increased basal release of amylase.

Blockage of cell-to-cell communication within pancreatic acini is associated with increased basal release of amylase.

Structure of rapidly frozen gap junctions.

Electrophysiology of Salivary and Pancreatic Acinar Cells

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