Changes in elemental concentrations of rat parotid acinar cells following pilocarpine stimulation.

Izutsu, Kenneth T.; Johnson, Dale E.

doi:10.1113/jphysiol.1986.sp016328

Cited by 32 publications

(22 citation statements)

References 25 publications

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“…These microprobe findings are consistent with other studies performed using isolated secretory granules that found that rat parotid secretory granules are permeable to K, Na, and C1 ions (Gasser et al, 1988a,b). In addition, the findings from our EPXMA study of isolated secretory granules (Izutsu et al, 1991a) also indicate that secretory granules are permeable to the diffusible ions, because the concentrations of K, Na, and C1 are significantly altered in isolated secretory granules when compared with granules in vivo ( Table 4; Izutsu and Johnson, 1986). Such changes probably reflect diffusive loss or gain of ions from granules during the isolation procedures, and are a reflection of the membrane permeability and electrochemical gradients of the three ions.…”

Section: Electron Probe X-ray Microanalysismentioning

confidence: 78%

“…EPXMA has also been used to determine how elemental concentrations in different intracellular organelles are affected by parasympathomimetic stimulation. Our initial studies of rat parotid acinar cells stimulated in situ indicated that cytoplasmic and nuclear K concentrations decreased while those of Na increased and those of C1 remained unchanged following stimulation with pilocarpine (Izutsu and Johnson, 1986). However, the experiments contained several limitations: (1) the concentration of pilocarpine at the gland was unknown because an intraperitoneal dose was administered, (2) secondary systemic effects of pilocarpine, for example, on the blood supply, could not be evaluated, and (3) the effects of sample excision on cell integrity could not be evaluated except by obvious morphological changes.…”

Section: Electron Probe X-ray Microanalysismentioning

confidence: 96%

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A review of electron probe X‐ray microanalysis studies of salivary gland cells

Izutsu

Cantino

Johnson

1994

Microscopy Res & Technique

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Electron probe X-ray microanalysis (EPXMA) has now been successfully applied to several salivary gland preparations. This paper briefly reviews the principles underlying this technique and the specific sample preparation procedures which permit accurate measurement of elemental concentrations in the various intracellular spaces. Findings from salivary gland studies indicate that cytoplasmic and nuclear spaces of nonstimulated acinar cells have high concentrations of K and P, and low concentrations of Mg, Ca, and S; and that mature secretory granules have high concentrations of Ca and S, and relatively low concentrations of K and P. No consistent differences have been found between the elemental concentrations of mucous and serous secretory granules. In vivo and in vitro EPXMA studies of the elemental changes associated with secretory granule maturation indicate there are at least two stages in this process: an early stage during which granule S concentration increases in parallel with mass density as condensing vacuoles mature into secretory granules, and a late stage during which granule mass density and protein content increase with no further elemental concentration changes. Findings from other in vivo and in vitro studies indicate that secretory granule membranes are permeable to Na, K, and Cl ions because the granular concentrations of these elements are altered by electrochemical gradients. Recent EPXMA results indicate that cells stimulated with parasympathomimetic agonists have decreased K and Cl concentrations, and increased Na concentrations. Furthermore, the magnitude of these changes are quantitatively consistent with changes measured using radio-isotope equilibration and other techniques. In contrast, cells stimulated with the beta-adrenergic agonist, isoproterenol, have increased concentrations of Na and Cl, but unchanged K concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Electron Probe X-ray Microanalysismentioning

confidence: 78%

Section: Electron Probe X-ray Microanalysismentioning

confidence: 96%

A review of electron probe X‐ray microanalysis studies of salivary gland cells

Izutsu

Cantino

Johnson

1994

Microscopy Res & Technique

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“…The high Ca content of ASGs may represent a property common to many (e.g., refs. 33 and 34), but not all, secretory vesicles generated by the Golgi apparatus. In ASGs, it probably reflects Ca binding to the ANF prohormone that is the major protein component ofisolated granules (4).…”

Section: Discussionmentioning

confidence: 96%

Atrial-specific granules in situ have high calcium content, are acidic, and maintain anion gradients.

Somlyo

Broderick

Shuman

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

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The composition and pH of atrial-specific granules of rat heart were determined by electron probe x-ray microanalysis and fluorescence microscopy, respectively. The high (75 mmol/kg of dry weight) calcium content and higher than cytoplasmic concentration of chloride in atrial-specific granules were visualized in high-resolution x-ray maps. The C1-content of granules and cytoplasm decreased and a bromide gradient (granule > cytoplasm) was established during incubation in low-chloride, NaBr-containing solutions.Scanning confocal fluorescence light microscopy of live atria incubated with acridine orange demonstrated dye accumulation, indicative of low intragranular pH. We conclude that the granules represent a hitherto unrecognized intracellular store of cardiac calcium and can develop and maintain an anion gradient, presumably through cotransport by means of a proton-pumping ATPase.Atrial-specific granules (ASGs), described nearly three decades ago and present in the heart of most vertebrates (1, 2), contain precursors of a family of vasodilator and natriuretic polypeptides, collectively called atrial natriuretic factor (ANF) (3-7). The heart can function as an endocrine organ, releasing ANF in response to changes in atrial distending pressure and other stimuli (8). We now show that ASGs share other properties of endocrine secretory granules, such as an acidic interior and the ability to establish a sizable anion gradient. We also show that these organelles have a high Ca content and are a hitherto unknown store of intracellular Ca in atrial myocardium. Based on the known sequences ofANF prohormone (9, 10) and the Ca-binding protein calsequestrin (11), we suggest that the high Ca content of ASGs is probably due to binding to grouped acidic residues in the aminoterminal sequence of the prohormone. METHODS AND MATERIALSMale Wistar rats (250-300 g of body weight) were killed by cervical dislocation, and the hearts were quickly excised and placed in a well-oxygenated modified Krebs/bicarbonate solution (pH 7.4) at 32°C containing (mM) NaCl, 125; KCI, 4.7; KH2PO4, 1.2; MgSO4, 1.2; NaHCO3, 18.7; CaCl2, 1.2; dextrose, 5.6. The right atrium was everted over a 1.5-mm (diameter) silver pin and tied at the base. Tension was not monitored. The atria in Krebs solution generally beat spontaneously up to the point of freezing in either systole or diastole. To determine whether ASGs can establish an anion gradient de novo, atria were incubated for 15 min at 32°C in a solution (pH 7.4) containing (mM) sodium methanesulfonate, 105; NaBr, 20; potassium methanesulfonate, 4.7;

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“…Also consistent with the presence of ATP in lamellar body are the borderline significant changes in magnesium content prenatally, and the significant correlation of phosphorus and magnesium in all prenatal intracellular lamellar bodies (Table IV). An alternative explanation for this significant increase in lamellar body phosphorus in the prenatal period would be a major shift in the phospholipid class, a possibility which has not been supported by biochemical approaches (32 (38), but consistent with what is found in the cytoplasm of other secretory cells when using EPMA of freeze-dried cryosections (39,40). The relatively-high total calcium content of the cytoplasm in these secretory cells has been attributed to the densely distributed endoplasmic reticulum (ER), which is generally not visualized in cryosections, and which is known to accumulate and release calcium in a fashion similar to SR (39,41).…”

Section: Discussionmentioning

confidence: 88%

“…An alternative explanation for this significant increase in lamellar body phosphorus in the prenatal period would be a major shift in the phospholipid class, a possibility which has not been supported by biochemical approaches (32 (38), but consistent with what is found in the cytoplasm of other secretory cells when using EPMA of freeze-dried cryosections (39,40). The relatively-high total calcium content of the cytoplasm in these secretory cells has been attributed to the densely distributed endoplasmic reticulum (ER), which is generally not visualized in cryosections, and which is known to accumulate and release calcium in a fashion similar to SR (39,41). Thus, the increase in "cytoplasmic") calcium content in this perinatal period probably reflects either an increased density/volume of the ER, an increase in ER calcium binding capacity or an increased activity of the ER calcium transporting system.…”

Section: Discussionmentioning

confidence: 88%

Perinatal changes in lung surfactant calcium measured in situ.

Eckenhoff¹

1989

J. Clin. Invest.

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Calcium ion is thought to play a role in the structure and function of pulmonary surfactant after secretion into the alveolar space. Since fetal lung liquid calcium concentration is inadequate for this hypothesized role, at a time when optimal surfactant function is necessary for survival, we speculated that the necessary calcium is secreted with the surfactant material, i.e., in the lamellar body. Lungs from rat fetuses at 20, 21, and 22 d gestation, and also from newborn rats at 3-5 h, 1 and 3 d, were rapidly frozen, sectioned, freeze-dried, and examined cold (-100°C) in a transmission electron microscope equipped with a fully quantitative energy-dispersive x-ray detector and analyzer. X-ray spectra were collected from the lamellar bodies and cytoplasm of type II cells at each time point. Lamellar body calcium concentration in the fetus was approximately twice that of the adult (70±4 vs. 37±2 mmol/kg dry wt±SEM, P < 0.01), and it decreased rapidly after birth to adult levels. Apically located lamellar bodies in the fetus have a significantly higher calcium concentration than those in a perinuclear position (76±4 vs. 52±3, P < 0.01). There is a significant correlation of calcium and chloride concentrations in lamellar bodies, suggesting that factors responsible for the distribution of chloride, i.e., pH, may also be responsible for the accumulation of calcium by these organelles. These results show that mature calcium transport in lamellar bodies is achieved prenatally in the rat, and suggest that the calcium required for normal surfactant function at birth is secreted with the lamellar body.

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Changes in elemental concentrations of rat parotid acinar cells following pilocarpine stimulation.

Cited by 32 publications

References 25 publications

A review of electron probe X‐ray microanalysis studies of salivary gland cells

A review of electron probe X‐ray microanalysis studies of salivary gland cells

Atrial-specific granules in situ have high calcium content, are acidic, and maintain anion gradients.

Perinatal changes in lung surfactant calcium measured in situ.

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