Secretion of calcium in pancreatic juice.

Ceccarelli, B; Clémente, F.; Meldolesi, Jacopo

doi:10.1113/jphysiol.1975.sp010865

Cited by 38 publications

(25 citation statements)

References 32 publications

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“…These findings further confirm the idea that in the pancreas, as previously suggested in other secretory systems (Berneis et al, 1969;Wallach & Schramm, 1971), the role of the calcium segregated within the secretion granules might be concerned not with the regulation of the cellular activity but with the architecture of the granules themselves and with the functionality of the released secretion products Ceccarelli, Clemente & Meldolesi, 1975).…”

Section: Discussionsupporting

confidence: 79%

Calcium and Pancreatic Secretion‐dynamics of Subcellular Calcium Pools in Resting and Stimulated Acinar Cells

Clémente

Meldolesi

1975

British J Pharmacology

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I Pulse-chase experiments were carried out on pancreatic tissue lobules incubated in vitro, with 45Ca as the tracer, in order to shed some light on the functional significance of the calcium pools associated with the various cell organelles of the acinar cell, especially in relation to stimulus-secretion coupling. 2 The kinetics of tracer uptake and release which were observed in the intact lobules suggest the existence of a number of intracellular pools, whose rate of exchange is slower than that across the plasmalemma. 3 The various subcellular fractions accumulate the tracer in different amounts: some (rough microsomes and postmicrosomal supernatant) showed little radioactivity and some (smooth microsomes and zymogen granule membranes) were heavily labelled; mitochondria and zymogen granules showed intermediate values. 4 The fractions are heterogeneous also in relation to the time course of uptake and release of the tracer: in rough and smooth microsomes and, especially, in the postmicrosomal supernatant both rates were fast; zymogen granules and zymogen granule membranes showed slow rates of uptake and little release during chase; intermediate rates were found in mitochondria.5 In agreement with previous findings we observed that in 45Ca preloaded lobules, stimulation of secretion (brought about by the secretagogue polypeptide caerulein) results in an increase of the tracer release which seems to be due primarily to the rise of the intracellular concentration of free Ca2+ and to the consequent increase of the transmembrane Ca2+ efflux. Among the cell fractions isolated from stimulated lobules only the mitochondria exhibited a significantly lower 45Ca level relative to the unstimulated controls. 6 It is concluded that, of the organelle-bound calcium pools, that associated with the mitochondria might be involved in the regulation of the calcium-dependent functions, including stimulus-secretion coupling; the calcium associated with the zymogen granule content probably has a role in the architecture of the organelle and in the functionality of the pancreatic juice, while the calcium bound to the membrane of the granules might be concerned with the regulation of its permeability properties.

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Section: Discussionsupporting

confidence: 79%

Calcium and Pancreatic Secretion‐dynamics of Subcellular Calcium Pools in Resting and Stimulated Acinar Cells

Clémente

Meldolesi

1975

British J Pharmacology

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“…Other studies on the exocrine pancreas and parotid gland have also noted similarities in the composition of the secretary granules and gland secretion (Wallach'& Schramm, 1971;Ceccarelli, Clemente & Meldolesi, 1975 Wallach & Schramm (1971) have however, shown that only 14 % of the granule Ca2+ is tightly associated with proteins. There is also considerable evidence to suggest that the effects ofadrenergic and cholinergic stimulation on the movement ofexchangeable Ca2+ across the plasma membrane is independent of amylase secretion (Kanagasuntheram & Randle, 1976;Miller & Nelson, 1977;Kusek, 1978).…”

Section: Resultsmentioning

confidence: 99%

parallel secretion of secretory proteins and calcium by the rat parotid gland.

Kanagasuntheram¹,

Lim²

1981

The Journal of Physiology

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SUMMARY1. The secretion of amylase, deoxyribonuclease, ribonuclease, protein and Ca2+ by the rat parotid gland in vitro was studied.2. Isoproterenol and carbamoyleholine elicited a parallel discharge of amylase, deoxyribonuclease, ribonuclease and protein over a 40 min time period.3. The composition of the secretion was independent of the secretogogue used for stimulation. When gland slices from the same animal were stimulated with isoproterenol, adrenaline, phenylephrine or carbamoyleholine, secretary enzymes and protein were secreted in constant proportions.4. 45Ca injected intraperitoneally 16 h before stimulation with either isoproterenol or carbamoyleholine was released in parallel with amylase and protein.5. The relative proportions of amylase, ribonuclease, deoxyribonuclease, protein and Ca present in isolated parotid gland secretary granules was identical to that of isoproterenol stimulated gland secretion.6. It is concluded that the secretary proteins and Ca2+ are discharged in constant proportions by the rat parotid gland regardless of the mode of stimulation or the rate of secretion. The similarity in the composition of gland secretion and granule contents also suggests that enzymes and Ca2+ are released by exocytosis and not by diffusion across the apical plasma membrane.

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“…The rest comes from different sources which might be either the interstitial fluid or a different pathway operating in the acinar cells, or both (56). The existence of multiple sources of calcium in the pancreatic secretion could be one of the numerous mechanisms which contribute to switch the conditions for the activation of the proteolytic zymogens from unfavorable, as in ZG, to favorable, as in the intestinal lumen.…”

Section: Discussionmentioning

confidence: 99%

Calcium and pancreatic secretion. I. Subcellular distribution of calcium and magnesium in the exocrine pancreas of the guinea pig.

Clémente¹,

Meldolesi²

1975

The Journal of Cell Biology

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117

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The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed among all the particulate fractions, primarily the mitochondria, microsomes (especially smooth surfaced), zymogen granules, and the plasmalemma, and was low in the postmicrosomal supernate. Most of the calcium recovered in the particulate fractions was found to be membrane bound. The highest concentrations were found in the membranes of the zymogen granules and in the plasmalemma.By means of control experiments using 'sCa as the tracer, it was established that a considerable redistribution of calcium occurs during homogenization and cell fractionation. At least some of the resulting artifacts were estimated quantitatively and the data were corrected accordingly. The biochemical results were confirmed with the cytochemical antimonate technique carried out on the tissue as well as on isolated fractions.The role of calcium associated with the zymogen granules and with their limiting membranes is discussed in relation to the architecture of the granule and to the functionality of the pancreatic juice.It has been clearly established in a number of cell systems that calcium plays an essential role in several steps of the secretory process (I 4). Thus, calcium appears to be involved (a) in the intracellular packaging of secretion products (5, 6), (b) in the regulation of the permeability of the plasmalemma, including the permeability changes occurring after stimulation of secretion (1-4, 7, 8), and (c) in the complex series of events which transduce the stimulation of the secretory cell into its specific secretory response (stimulus-secretion coupling) (1-4, 7 12).Since the pioneer work of Douglas and his associates on the adrenal medulla, the calcium acting in the stimulus-secretion coupling was assumed to be of extracellular origin (9 11). This

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Secretion of calcium in pancreatic juice.

Cited by 38 publications

References 32 publications

Calcium and Pancreatic Secretion‐dynamics of Subcellular Calcium Pools in Resting and Stimulated Acinar Cells

Calcium and Pancreatic Secretion‐dynamics of Subcellular Calcium Pools in Resting and Stimulated Acinar Cells

parallel secretion of secretory proteins and calcium by the rat parotid gland.

Calcium and pancreatic secretion. I. Subcellular distribution of calcium and magnesium in the exocrine pancreas of the guinea pig.

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