Cytochemical evidence for cation fluxes in parotid acinar cells following stimulation by isoproterenol

Simson, J. A. V.; Spicer, Samuel S.

doi:10.1002/ar.1091780202

Cited by 15 publications

(1 citation statement)

References 64 publications

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“…This interpretation is based on the assumption that calcium is compartmentalized within the secretory cells in a number of pools, whose size can be rapidly adjusted in relation to the functional activity. However, up to now this assumption has not been proven because only very few secretory systems have been studied in detail in order to elucidate the functional distribution of calcium within the cells (Borowitz, 1969;Rahwan, Borowitz & Miwa, 1973;Herman, Sato & Hales, 1973;Simpson & Spicer, 1974).…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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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Cations in the rat pars distalis ultrastructural localization

Schechter

1976

Am. J. Anat.

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Pituitary glands of female Sprague Dawley rats were fixed using the potassium pyroantimonate-osmium tetroxide technique by immersion or vascular perfusion. Both fixation procedures resulted in similar patterns of cation localization visualized as electron-dense precipitate within cells of the pars distalis. Nuclei were prominent sites of localization. Cytoplasmic precipitate occurred in association with the endoplasmic reticulum, typically within the cisternal spaces, and also was localized within the mitochondrial matrix and cristae, as well as Golgi membranes, small Golgi-associated vesicles, and multivesicular bodies. Immature secretory granules often contained precipitate between the core material of the granule and the enclosing smooth membrane. Frequently small antimonate-containing vesicles bordered the immature secretory granules. Precipitate was variable in secretory granules of more mature appearance although precipitate was apparent occasionally just within a granule's enclosing membrane. Granules closest to the plasma membrane often contained increased amounts of precipitate and small vesicles containing precipitate were observed fusing with them. Instances of granule release by emiocytosis often revealed a clustering of precipitate behind the core material away from the emiocytotic stoma, as well as at the stoma, and frequently an increased electron density of filamentous material radiating from the granules' enclosing membranes or from the adjacent plasma membrane. Exposure of section material to the chelating agents EGTA and EDTA indicate that calcium is the primary cation localized within the cytoplasm of these secretory cells. These findings are consistent with a role for calcium as a facilitator in the processes of transport and release of secretory granules.

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Cytochemical localization of cations in the testis of the syrian hamster, utilizing potassium‐pyroantimonate

Gravis

1979

Am. J. Anat.

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Pyroantimonate has long been used as a cytochemical technique for the localization of cations. Although the technique was originally alleged to be specific for Na+, other cations, including Mg++, Ba++, Ca++, Zn++ and polycationic amines, form pyroantimonate precipitates. In seminiferous tubules treated with antimonate-osmium fixation, the nuclei of the Sertoli cells and germ cells contained precipitates. In regions of condensed chromatin the precipitates were dense while, in dispersed chromatin, precipitates were sparse or absent. It is postulated that the dense precipitates observed in the condensed chromatin may represent an accumulation of calcium that may facilitate chromatin condensation. The Sertoli cell nucleolar apparatus contained light precipitates in the pars amorpha, moderate precipitates in the nucleolonema, and heavy precipitates in the perinucleolar heterochromatin bodies. The nuclei of the maturation-phase spermatids lacked any Precipitates. The perinuclear ring of the acrosome-phase spermatids contained pyroantimonate deposits. In the maturation-phase spermatids, staining occurred in the postacrosomal dense lamina, in the subacrosomal space between the perforatorium and the inner acrosomal membrane, and in the central mass of the residual bodies. Since the postacrosomal dense lamina is the portion of the spermatozoon that initially fuses with the ovum, it is postulated that its cationic properties in some way facilitate this fusion.Pyroantimonate is a unique anion which can be dissolved as the potassium salt but forms insoluble precipitates with other cations. The low molecular weight of pyroantimonate and its electron-opacity render it useful for ultrastructural localization of cations. Komnick ('62) was the first to use potassium pyroantimonate as a cytochemical technique for localization of cations. Although the method was originally alleged to be specific for the localization of sodium, it was later shown that other cations form pyroantimonate salts. Several lines of evidence indicate that pyroantimonate forms insoluble precipitates with B a + + , Ca++, Mg++, Na+, Zn++, glycogen, histamine, spermine, and histones; potassium-antimonate may form in sites of lowered pH or when the pH of the cytochemical medium is not properly controlled (Bulger, '69; Legato and Langer, '69; Lane and Martin, '69; Tisher et al., '69; Torack and LaValle, '70; Clark and Ackerman, '71; Klein et al., '72; Spicer and Swanson, '72).

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Cytochemical evidence for cation fluxes in parotid acinar cells following stimulation by isoproterenol

Cited by 15 publications

References 64 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

Cations in the rat pars distalis ultrastructural localization

Cytochemical localization of cations in the testis of the syrian hamster, utilizing potassium‐pyroantimonate

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