scholarly journals Intracellular pH regulates basolateral K+ and Cl- conductances in colonic epithelial cells by modulating Ca2+ activation.

1991 ◽  
Vol 98 (1) ◽  
pp. 183-196 ◽  
Author(s):  
D Chang ◽  
N L Kushman ◽  
D C Dawson
Keyword(s):  
Epithelial Cells ◽  
Intracellular Ph ◽  
Gain Control ◽  
Activation Process ◽  
Cytosolic Ph ◽  
Variable Gain ◽  
Ionic Conductances ◽  
Cell Layers ◽  
Conduction Properties

The role of intracellular pH as a modulator of basolateral K+ and Cl- conductances in epithelial cells was studied using digitonin-permeabilized colonic cell layers so that cytosolic pH could be clamped at specific values, while basolateral K+ and Cl- conductances were activated by stepwise increases in intracellular free Ca2+. Increasing the intracellular pH from 6.6 to 8.0 enhanced the sensitivity of both ionic conductances to intracellular Ca2+, but changing extracellular pH had no effect. Maximal K+ and Cl- currents activated by Ca2+ were not affected by changes in intracellular pH, suggesting that protons do not alter the conduction properties of the channels. Hill analysis of the Ca2+ activation process revealed that raising the cytosolic pH from 6.6 to 8.0 reduced the K1/2 for Ca2+ activation. In the absence of Ca2+, changes in intracellular pH did not have a significant effect on the basolateral K+ and Cl- conductances. These results are consistent with the notion that changes in cytosolic pH can modulate basolateral conductances by modifying the action of calcium, perhaps by acting at or near the activation site to provide a mechanism of variable "gain control."

Intracellular pH modulates cytosolic free magnesium in cultured chicken heart cells

1992 ◽  
Vol 262 (4) ◽  
pp. C1024-C1030 ◽  
Author(s):  
C. C. Freudenrich ◽  
E. Murphy ◽  
L. A. Levy ◽  
R. E. London ◽  
M. Lieberman
Keyword(s):  
Intracellular Ph ◽  
Total Cell ◽  
Transient Increase ◽  
Heart Cells ◽  
Cytosolic Ph ◽  
Chicken Heart ◽  
Subcellular Organelles ◽  
Nh4cl Solution ◽  
Free Magnesium

To assess the role of pH in cellular Mg homeostasis, cytosolic pH (pHi) was manipulated by the NH4Cl prepulse technique; pHi, cytosolic Mg2+ (Mgi), and cytosolic Ca2+ (Cai) were measured fluorometrically in single cultured embryonic chicken heart cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), FURAPTRA, and fura-2, respectively. The basal values obtained were as follows: pHi = 7.21 +/- 0.10 (n = 7), [Mg]i = 0.51 +/- 0.08 mM (n = 9), [Ca]i = 126 +/- 15 nM (n = 7). When cells were perfused with 10 mM NH4Cl solution for 5 min, a transient alkalinization (0.53 U) of the cytosol was accompanied by a transient decrease (0.12 mM) in [Mg]i and a transient increase (59 nM) in [Ca]i; these changes approached control levels within 5 min. Upon removal of NH4Cl, a transient acidification (0.89 U) of the cytosol was accompanied by a transient increase (0.10 mM) in [Mg]i and a transient increase (125 nM) in [Ca]i; again, these changes returned toward control levels within 5 min. No significant changes in total cell Mg or Ca were observed during these manipulations. NH4Cl-evoked changes in [Mg]i were not altered significantly by either Mg-free or Ca-free conditions. Changes in [Mg]i were inversely correlated with changes in pHi and were not secondary to changes in [Ca]i. The results suggest that pHi modulates Mgi, probably by affecting cytosolic Mg binding and/or the transport of Mg across subcellular organelles.

Inhibition of NHE protects reoxygenated cardiomyocytes independently of anoxic Ca2+ overload and acidosis

2000 ◽  
Vol 279 (5) ◽  
pp. H2143-H2150 ◽  
Author(s):  
C. Schäfer ◽  
Y. V. Ladilov ◽  
M. Schäfer ◽  
H. M. Piper
Keyword(s):  
Intracellular Ph ◽  
Cytosolic Ph ◽  
Bicarbonate Buffer ◽  
Rat Cardiomyocytes ◽  
Hepes Buffer ◽  
Adult Rat ◽  
Reoxygenation Injury ◽  
Sodium Binding ◽  
Cytosolic Acidification

We investigated the question of whether inhibition of the Na+/H+ exchanger (NHE) during ischemia is protective due to reduction of cytosolic Ca2+ accumulation or enhanced acidosis in cardiomyocytes. Additionally, the role of the Na+-HCO3 − symporter (NBS) was investigated. Adult rat cardiomyocytes were exposed to simulated ischemia and reoxygenation. Cytosolic pH [2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)], Ca2+ (fura 2), Na+ [sodium-binding benzolfuran isophthatlate (SBFI)], and cell length were measured. NHE was inhibited with 3 μmol/l HOE 642 or 1 μmol/l 5-( N-ethyl- N-isopropyl)-amiloride (EIPA), and NBS was inhibited with HEPES buffer. During anoxia in bicarbonate buffer, cells developed acidosis and intracellular Na and Ca (Nai and Cai, respectively) overload. During reoxygenation cells underwent hypercontracture (44.0 ± 4.1% of the preanoxic length). During anoxia in bicarbonate buffer, inhibition of NHE had no effect on changes in intracellular pH (pHi), Nai, and Cai, but it significantly reduced the reoxygenation-induced hypercontracture (HOE: 61.0 ± 1.4%, EIPA: 68.2 ± 1.8%). The sole inhibition of NBS during anoxia was not protective. We conclude that inhibition of NHE during anoxia protects cardiomyocytes against reoxygenation injury independently of cytosolic acidification and Cai overload.

scholarly journals Role of lysosomal and cytosolic pH in the regulation of macrophage lysosomal enzyme secretion

1990 ◽  
Vol 272 (2) ◽  
pp. 407-414 ◽  
Author(s):  
H Tapper ◽  
R Sundler
Keyword(s):  
Intracellular Ph ◽  
Fluorescent Probes ◽  
Lysosomal Enzyme ◽  
Enzyme Secretion ◽  
Relative Role ◽  
Ion Composition ◽  
Cytosolic Ph ◽  
Lysosomal Ph ◽  
Cytosolic Acidification

Rapid and parallel secretion of lysosomal beta-N-acetylglucosaminidase and preloaded fluorescein-labelled dextran was initiated in macrophages by agents affecting intracellular pH (methylamine, chlorpromazine, and the ionophores monensin and nigericin). In order to evaluate the relative role of changes in lysosomal and cytosolic pH, these parameters were monitored by using pH-sensitive fluorescent probes [fluorescein-labelled dextran or 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein]. All agents except chlorpromazine caused large increases in lysosomal pH under conditions where they induced secretion. By varying extracellular pH and ion composition, the changes in lysosomal and cytosolic pH could be dissociated. Secretion was then found to be significantly modulated by changes in cytosolic pH, being enhanced by alkalinization and severely inhibited by cytosolic acidification. However, changes in cytosolic pH in the absence of stimulus were unable to initiate secretion. Dissociation of the effects on lysosomal and cytosolic pH was also achieved by combining stimuli with either nigericin or acetate. Further support for a role of intracellular pH in the control of lysosomal enzyme secretion was provided by experiments where bicarbonate was included in the medium. The present study demonstrates that an increase in lysosomal pH is sufficient to initiate lysosomal enzyme secretion in macrophages and provides evidence for a significant regulatory role of cytosolic pH.

Characterization of Na+-H+ antiport in type II alveolar epithelial cells

1987 ◽  
Vol 252 (5) ◽  
pp. C490-C498 ◽  
Author(s):  
E. P. Nord ◽  
S. E. Brown ◽  
E. D. Crandall
Keyword(s):  
Epithelial Cells ◽  
Intracellular Ph ◽  
Cell Types ◽  
Alveolar Epithelial Cells ◽  
Hill Coefficient ◽  
Type Ii ◽  
Transport Pathway ◽  
Cytosolic Ph ◽  
Alveolar Epithelial ◽  
Major Mechanism

The presence of a Na+-H+ exchange pathway in the plasma membrane of type II alveolar epithelial cells was explored using the pH-sensitive fluorescent probe 2,7-biscarboxyethyl-5,6-carboxyfluorescein (BCECF) to monitor changes in cytosolic pH. Freshly prepared pneumocytes suspended in medium at pH 7.4 had an intracellular pH of 7.07 +/- 0.07. Acid-loaded cells equilibrated in sodium-free buffer showed rapid cytoplasmic alkalinization when exposed to sodium. This response to sodium was inhibited greater than 90% by 10(-4) M amiloride. The presence of the K+ ionophore, valinomycin, had no effect on the rate of Na+-dependent alkalinization, indicating the electroneutrality of the system. Li+ partially supported the alkalinization process, but other monovalent cations, notably K+, Rb+, and Cs+, were without effect. Kinetic analysis for Na+ at the external binding site yielded KNat (dissociation constant) = 62 +/- 3 mM. Hill equation analysis of the data derived a Hill coefficient (n) = 1.2 +/- 0.1 for Na+, consistent with a 1:1 stoichiometry for Na+ and H+ for the transporter. The Ki for amiloride inhibition of proton efflux at the external locus was 0.45 microM. These findings define the transport pathway as Na+-H+ antiport, with kinetic parameters somewhat similar to those described for other cell types. Antiport activity was detected at intracellular pH (pHi) values of 6.8 or below, with no activity observed at pHi 7.0-7.2. It is suggested that Na+-H+ exchange is a major mechanism whereby pneumocytes recover from an acid load and that this transport pathway may play an important role in vectorial reabsorption of Na+ from the alveolar air spaces.

The role of acid phosphatase in the fusion of the secondary palate

Development ◽  
1968 ◽  
Vol 20 (1) ◽  
pp. 15-23
Author(s):  
D. Angelici ◽  
M. Pourtois
Keyword(s):  
Electron Microscopy ◽  
Acid Phosphatase ◽  
Epithelial Cells ◽  
Organ Culture ◽  
Fusion Process ◽  
Culture Methods ◽  
Secondary Palate ◽  
Subsequent Step ◽  
Cell Layers

Complete closure of the secondary palate must progress through two consecutive events: the converging movement of the palatal shelves and their subsequent fusion at the line of contact. Each step is indispensable in normal palatal development since, theoretically, a palatal cleft might be the consequence of a failure of either. Until recently, the mechanisms of shelf movement received most attention (Peter, 1924; Lazarro, 1940; Walker & Fraser, 1956; Larsson, 1960). However, recent investigations have focused on the subsequent step, properly referred to as fusion. These studies, based on organ culture methods (Pourtois, 1966) and electron microscopy (Mato, Aikawa & Katahira, 1966; Farbman, 1967; Smiley & Dixon, 1967), have emphasized the complexity of the fusion process. This process may be viewed as a sequence of four interdependent events: (1) differentiation of the cell layers at the edge of the shelves resulting in the formation of a ‘zone of stickiness’ (Pourtois, 1968); (2) fusion of these differentiated epithelial cells leading to the formation of a laminated wall of epithelium between the shelves; (3) rupture of that partition permitting contact between the elements of the mesenchyme from either side; and (4) finally, degeneration of the epithelial remains of the seam marking the completion of the fusion process.

Video-Enhanced Microscopy--Better Visibility of Plant Cell Structures

1982 ◽  
Vol 40 ◽  
pp. 182-185
Author(s):  
N.S. Allen ◽  
R.D. Allen
Keyword(s):  
Diffraction Pattern ◽  
Theoretical Basis ◽  
Numerical Aperture ◽  
Gain Control ◽  
Control Unit ◽  
Camera Control ◽  
Variable Gain ◽  
Contrast Method ◽  
Fine Detail ◽  
Cell Structures

Various methods of video-enhanced microscopy combine TV cameras with light microscopes creating images with improved resolution, contrast and visibility of fine detail, which can be recorded rapidly and relatively inexpensively. The AVEC (Allen Video-enhanced Contrast) method avoids polarizing rectifiers, since the microscope is operated at retardations of λ/9- λ/4, where no anomaly is seen in the Airy diffraction pattern. The iris diaphram is opened fully to match the numerical aperture of the condenser to that of the objective. Under these conditions, no image can be realized either by eye or photographically. Yet the image becomes visible using the Hamamatsu C-1000-01 binary camera, if the camera control unit is equipped with variable gain control and an offset knob (which sets a clamp voltage of a D.C. restoration circuit). The theoretical basis for these improvements has been described.

The Ultrastructure of Monkey Gingival Epithelium

1967 ◽  
Vol 25 ◽  
pp. 16-17
Author(s):  
C.N. Sun
Keyword(s):  
Epithelial Cells ◽  
Macaca Nemestrina ◽  
Stratum Granulosum ◽  
Solution Ph ◽  
Gingival Epithelial Cells ◽  
Stratum Spinosum ◽  
Cell Layers ◽  
Gingival Epithelium ◽  
The Individual ◽  
Different Thickness

The present study demonstrates the ultrastructure of the gingival epithelium of the pig tail monkey (Macaca nemestrina). Specimens were taken from lingual and facial gingival surfaces and fixed in Dalton's chrome osmium solution (pH 7.6) for 1 hr, dehydrated, and then embedded in Epon 812.Tonofibrils are variable in number and structure according to the different region or location of the gingival epithelial cells, the main orientation of which is parallel to the long axis of the cells. The cytoplasm of the basal epithelial cells contains a great number of tonofilaments and numerous mitochondria. The basement membrane is 300 to 400 A thick. In the cells of stratum spinosum, the tonofibrils are densely packed and increased in number (fig. 1 and 3). They seem to take on a somewhat concentric arrangement around the nucleus. The filaments may occur scattered as thin fibrils in the cytoplasm or they may be arranged in bundles of different thickness. The filaments have a diameter about 50 A. In the stratum granulosum, the cells gradually become flatted, the tonofibrils are usually thin, and the individual tonofilaments are clearly distinguishable (fig. 2). The mitochondria and endoplasmic reticulum are seldom seen in these superficial cell layers.

Effect of Calcium on the Growth and Differentiation of Cultured Rat Esophageal Epithelial Cells

1982 ◽  
Vol 40 ◽  
pp. 132-133
Author(s):  
W.T. Gunning ◽  
M.R. Marino ◽  
M.S. Babcock ◽  
G.D. Stoner
Keyword(s):  
Epithelial Cells ◽  
Cell Types ◽  
Replication Rate ◽  
Enzymatic Dissociation ◽  
Growth Assay ◽  
Epidermal Growth ◽  
Fetal Bovine ◽  
Esophageal Epithelial Cells ◽  
Cellular Replication

The role of calcium in modulating cellular replication and differentiation has been described for various cell types. In the present study, the effects of Ca++ on the growth and differentiation of cultured rat esophageal epithelial cells was investigated.Epithelial cells were isolated from esophagi taken from 8 week-old male CDF rats by the enzymatic dissociation method of Kaighn. The cells were cultured in PFMR-4 medium supplemented with 0.25 mg/ml dialyzed fetal bovine serum, 5 ng/ml epidermal growth factor, 10-6 M hydrocortisone 10-6 M phosphoethanolamine, 10-6 M ethanolamine, 5 pg/ml insulin, 5 ng/ml transferrin, 10 ng/ml cholera toxin and 50 ng/ml garamycin at 36.5°C in a humidified atmosphere of 3% CO2 in air. At weekly intervals, the cells were subcultured with a solution containing 1% polyvinylpyrrolidone, 0.01% EGTA, and 0.05% trypsin. After various passages, the replication rate of the cells in PFMR-4 medium containing from 10-6 M to 10-3 M Ca++ was determined using a clonal growth assay.

Role of Bronchial Epithelial Cells in Pathogenesis of COPD

Pneumologie ◽  
2011 ◽  
Vol 65 (12) ◽  
Author(s):  
S Rim ◽  
S Jahan ◽  
G John ◽  
K Kohse ◽  
A Bohla ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Bronchial Epithelial Cells ◽  
Bronchial Epithelial
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