Timolol may inhibit aqueous humor secretion by cAMP-independent action on ciliary epithelial cells

2001 ◽  
Vol 281 (3) ◽  
pp. C865-C875 ◽  
Author(s):  
Charles W. McLaughlin ◽  
David Peart ◽  
Robert D. Purves ◽  
David A. Carré ◽  
Kim Peterson-Yantorno ◽  
...  
Keyword(s):  
Aqueous Humor ◽  
Ciliary Epithelium ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
X Ray ◽  
Transport Effect ◽  
Adrenergic Antagonist ◽  
Intracellular Ca ◽  
Epithelial Secretion ◽  
Cell Sizing

The β-adrenergic antagonist timolol reduces ciliary epithelial secretion in glaucomatous patients. Whether inhibition is mediated by reducing cAMP is unknown. Elemental composition of rabbit ciliary epithelium was studied by electron probe X-ray microanalysis. Volume of cultured bovine pigmented ciliary epithelial (PE) cells was measured by electronic cell sizing; Ca2+ activity and pH were monitored with fura 2 and 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, respectively. Timolol (10 μM) produced similar K and Cl losses from ciliary epithelia in HCO[Formula: see text]/CO2 solution but had no effect in HCO[Formula: see text]/CO2-free solution or in HCO[Formula: see text]/CO2 solution containing the carbonic anhydrase inhibitor acetazolamide. Inhibition of Na+/H+ exchange by dimethylamiloride in HCO[Formula: see text]/CO2 solution reduced Cl and K comparably to timolol. cAMP did not reverse timolol's effects. Timolol (100 nM, 10 μM) and levobunolol (10 μM) produced cAMP-independent inhibition of the regulatory volume increase (RVI) in PE cells and increased intracellular Ca2+ and pH. Increasing Ca2+ with ionomycin also blocked the RVI. The results document a previously unrecognized cAMP-independent transport effect of timolol. Inhibition of Cl−/HCO[Formula: see text] exchange may mediate timolol's inhibition of aqueous humor formation.

Ion transport asymmetry and functional coupling in bovine pigmented and nonpigmented ciliary epithelial cells

1994 ◽  
Vol 266 (5) ◽  
pp. C1210-C1221 ◽  
Author(s):  
J. L. Edelman ◽  
G. Sachs ◽  
J. S. Adorante
Keyword(s):  
Transport Properties ◽  
Aqueous Humor ◽  
Lucifer Yellow ◽  
Regulatory Volume Decrease ◽  
Ciliary Epithelium ◽  
Functional Coupling ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Cell Sizing ◽  
Volume Decrease

The solute and water transport properties of the bovine ciliary epithelium were studied using isolated pigmented (PE) and nonpigmented (NPE) cells. It was shown that these cells were functionally coupled by demonstrating dye diffusion between paired PE and NPE cells after microinjection of lucifer yellow. Electronic cell sizing was used to measure cell volume changes of isolated PE and NPE cells in suspension after anisosmotic perturbations and after transport inhibition under isosmotic conditions. The PE cells showed the presence of a regulatory volume increase when subjected to osmotic shrinkage with NaCl, whereas the NPE cells did not demonstrate a regulatory volume increase under these conditions. In contrast, the NPE cells exhibited a regulatory volume decrease when subjected to osmotic swelling, whereas the PE cells did not recover from swelling. The regulatory volume decrease in NPE cells was inhibited by increased bath K or pretreatment with quinine (1 mM). The presence of a bumetanide-sensitive mechanism capable of moving measurable amounts of solute and water, probably Na-K-2Cl cotransport, was demonstrated in the PE cells but absent in the NPE cells. Bumetanide produced a dose-dependent shrinkage of PE cells at concentrations as low as 1 microM. Isosmotically reducing bath Cl, Na, or K concentration caused a rapid shrinkage of PE cells that was bumetanide inhibitable. The asymmetry of transport properties in PE and NPE cells supports a functional syncytium model of aqueous humor formation (39) across the two layers of the ciliary epithelium wherein ion uptake from the blood is carried out by the PE cells and ion extrusion by the NPE cells. Gap-junction coupling between the cells allows the ions taken up by the PE cells to move into the NPE cells. Extrusion of Na by the Na-K pump across the aqueous facing (basolateral) membranes of the NPE cells, most likely accompanied by Cl, determines the formation of the aqueous humor.

Effect of coupling on volume-regulatory response of ciliary epithelial cells suggests mechanism for secretion

1999 ◽  
Vol 276 (6) ◽  
pp. C1432-C1438 ◽  
Author(s):  
V. E. Walker ◽  
J. W. Stelling ◽  
H. E. Miley ◽  
T. J. C. Jacob
Keyword(s):  
Benzoic Acid ◽  
Aqueous Humor ◽  
Single Cells ◽  
Cell Swelling ◽  
Ciliary Epithelium ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Osmotic Challenge ◽  
The Times ◽  
Nonpigmented Ciliary Epithelial

The ciliary epithelium of the eye secretes the aqueous humor. It is a double epithelium arranged so that the apical surfaces of the nonpigmented ciliary epithelial (NPCE) and pigmented ciliary epithelial (PCE) cells face each other and the basolateral membranes face the inside of the eye and the blood, respectively. We have investigated the volume responses of both single cells and coupled pairs from this tissue to osmotic challenge. Both NPCE and PCE cells undergo regulatory volume increase (RVI) and decrease (RVD) when exposed to hyper- and hyposmotic solution, respectively. In hyposmotic solution single cells swell and return to their original volumes within ∼3 min. In nonpigmented cells RVD could be inhibited by blockers of volume-activated Cl−channels [tamoxifen (100%) > quinidine (87%) > DIDS (84%) > 5-nitro-2-(3-phenylpropylamino)benzoic acid (80%) > SITS (58%)] and K+ channels [Ba2+(31%)]. However, in PCE cells these inhibitors and additionally tetraethylammonium and Gd3+ were without effect. Only bumetanide, an inhibitor of Na+-K+-2Cl−cotransport, was found to have any effect on RVD in PCE cells. NPCE-PCE cell coupled pairs also underwent RVD, but with altered kinetics. The onset of RVD of the PCE cell in a pair occurred ≈80 s before that of the NPCE cell, and the peak swell was reduced. This is consistent with fluid movement from the PCE to the NPCE cell. The effect of the volume-activated Cl− channel inhibitor tamoxifen was to eliminate this difference in the times of onset of RVD in coupled cell pairs and to inhibit RVD in both the NPCE and PCE cells partially. On the basis of these observations we suggest that fluid is transferred from the PCE to the NPCE cell in coupled pairs during cell swelling and the subsequent RVD. Furthermore, we speculate that reciprocal RVI-RVD could underlie aqueous humor secretion.

Regulatory volume increase in mammalian jejunal villus cells is due to bumetanide-sensitive NaKCl2 cotransport

1990 ◽  
Vol 258 (5) ◽  
pp. G665-G674 ◽  
Author(s):  
R. J. MacLeod ◽  
J. R. Hamilton
Keyword(s):  
Cell Swelling ◽  
Disulfonic Acid ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Direct Measurements ◽  
Villus Cell ◽  
Kg Medium ◽  
Cell Sizing ◽  
Phosphate Buffered Saline ◽  
86Rb Influx

We assessed ion transport mechanisms operative during regulatory volume increase (RVI) in villus enterocytes isolated in suspension from guinea pig jejunum and examined with electronic cell sizing and 86Rb influx. After validation of the electronic-sizing technique with direct measurements of cell water, the response of cell volume to hypertonic media was evaluated in detail. When shrunk by exposure to hyperosmotic media (455 mosmol/kg medium) cells demonstrated a RVI that was complete in 20 min. RVI required extracellular Na+, K+, and Cl-; this cell swelling showed the following ion sensitivity; Na+ greater than Li+ greater than choline, K+ = Rb+, and Cl- greater than or equal to Br- greater than NO3- = acetate = gluconate. Bumetanide inhibition of villus cell swelling was concentration dependent from 10(-10) to 10(-5) M (7.0 +/- 4.5% vs. 87.8 +/- 0.3%); furosemide (10(-3)M) inhibited RVI (74.1 +/- 9.5%), but amiloride (10(-4) M) had little effect on cell swelling. Disulfonic stilbenes, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (10(-4) M), generated the same inhibition of RVI in either nominally HCO3(-)-free phosphate-buffered saline (PBS) or HCO3(-)-buffered PBS, suggesting anion exchange was not involved. Ouabain (10(-4) M) stimulated cell swelling. Hypertonic shrinkage increased the initial rate of bumetanide-sensitive 86Rb influx (80 +/- 38 vs. 1,011 +/- 241 pmol.mg protein-1.min-1; P less than 0.005) and required extracellular Na+ and Cl- (11 +/- 16 vs. 28 +/- 61 pmol.mg protein-1.min-1). RVI was prevented in low-K+ media (0.2 mM), but the addition of KCl initiated cell swelling. Our data strongly suggest that RVI in jejunal villus enterocytes occurs because of the hypertonic activation of NaKCl2 cotransport.

Separate control of regulatory volume increase and Na+-H+ exchange by cultured renal cells

1988 ◽  
Vol 255 (1) ◽  
pp. C76-C85 ◽  
Author(s):  
M. H. Montrose ◽  
C. Knoblauch ◽  
H. Murer
Keyword(s):  
Epithelioid Cell ◽  
Cell Shrinkage ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Opossum Kidney ◽  
Solute Uptake ◽  
Separate Control ◽  
Kg Medium ◽  
Cell Sizing ◽  
Cellular Acidification

Suspensions of OK cells (a continuous epithelioid cell line from opossum kidney) are examined by electronic cell sizing, measurements of intracellular pH, and measurements of cellular Na+ and K+. The response of the cells to hypertonic solutions is evaluated in most detail. When shrunken by exposure to hyperosmotic medium (430 mosmol/kg), the cells do not demonstrate a regulatory volume increase (RVI) independent of the solute that is used to increase osmolality [NaCl, N-methyl-D-glucamine-HCl (NMGCl), or sucrose]. In contrast, when cells are preexposed to 190 mosmol/kg medium and then shrunken by exposure to 310 mosmol/kg medium, a volume increase is observed after the addition of 120 mosmol/kg NaCl or NMGCl, but not sucrose. This RVI is sensitive to 1 mM furosemide and removal of Na+ or K+ from the medium, but it is not inhibited by 1 mM amiloride. In the presence of a propionate-induced cellular acidification, a Na+-H+ exchanger in the cells is shown to have a large capacity for net solute uptake and to be inhibited by 1 mM amiloride. Net solute uptake by the Na+-H+ exchanger is sensitive to addition of parathyroid hormone or 8-bromoadenosine 3',5'-cyclic monophosphate but is not stimulated in response to cell shrinkage.

The effect of Al/Si disorder on the bulk moduli of plagioclase feldspars

2010 ◽  
Vol 74 (6) ◽  
pp. 943-950 ◽  
Author(s):  
L. M. Sochalski-Kolbus ◽  
R. J. Angel ◽  
F. Nestola
Keyword(s):  
Bulk Modulus ◽  
Single Crystal ◽  
Equations Of State ◽  
X Ray Diffraction ◽  
Volume Increase ◽  
X Ray ◽  
Density Decrease ◽  
The Relationship

AbstractThe volumes of a disordered An20 (Qod = 0.15), a disordered An78 (Qod = 0.55) and an ordered An78 (Qod = 0.81) were determined up to 9.569(10) GPa, 8.693(5) GPa and 9.765(10) GPa, respectively, using single-crystal X-ray diffraction. The volume variations with pressure for these samples are described with 4th-order Birch Murnaghan equations of state with V0 = 669.88(7) Å3, K0 = 59.7(7) GPa. K′ = 5.7(5), K″ = −0.8(2) GPa−1 for disordered An20, V0 = 1340.48(10) Å3, K0 = 77.6(5) GPa, K0′ = 4.0(3), K″ = -0.59(9) GPa−1 for disordered An78 and V0 = 1339.62(6) A3, K0 = 77.4(6) GPa, K′ = 4.2(4), and K″ = −0.7(1) GPa−1 for ordered An78. Along with data from previous studies (An0 ordered, An0 disordered and An2o ordered), the volumes for the disordered samples were found to be up to ∼0.3% larger than the ordered samples of the same composition. The disordered samples are softer than the ordered samples of the same composition by 4(1)% for An0, 2.5(9)% for An20 and essentially zero for An78. The relationship between volume increase, density decrease, and decreasing bulk modulus with increasing disorder is in accordance with Birch's Law.

scholarly journals Hypertonic stress increases the Na+ conductance of rat hepatocytes in primary culture.

1995 ◽  
Vol 105 (4) ◽  
pp. 507-535 ◽  
Author(s):  
F Wehner ◽  
H Sauer ◽  
R K Kinne
Keyword(s):  
Cell Membrane ◽  
Primary Culture ◽  
Regulatory Volume Decrease ◽  
Rat Hepatocytes ◽  
Laser Scanning Microscopy ◽  
Specific Cell ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Hypertonic Stress ◽  
Cell Volumes

We studied the ionic mechanisms underlying the regulatory volume increase of rat hepatocytes in primary culture by use of confocal laser scanning microscopy, conventional and ion-sensitive microelectrodes, cable analysis, microfluorometry, and measurements of 86Rb+ uptake. Increasing osmolarity from 300 to 400 mosm/liter by addition of sucrose decreased cell volumes to 88.6% within 1 min; thereafter, cell volumes increased to 94.1% of control within 10 min, equivalent to a regulatory volume increase (RVI) by 44.5%. This RVI was paralleled by a decrease in cell input resistance and in specific cell membrane resistance to 88 and 60%, respectively. Ion substitution experiments (high K+, low Na+, low Cl-) revealed that these membrane effects are due to an increase in hepatocyte Na+ conductance. During RVI, ouabain-sensitive 86Rb+ uptake was augmented to 141% of control, and cell Na+ and cell K+ increased to 148 and 180%, respectively. The RVI, the increases in Na+ conductance and cell Na+, as well as the activation of Na+/K(+)-ATPase were completely blocked by 10(-5) mol/liter amiloride. At this concentration, amiloride had no effect on osmotically induced cell alkalinization via Na+/H+ exchange. When osmolarity was increased from 220 to 300 mosm/liter (by readdition of sucrose after a preperiod of 15 min in which the cells underwent a regulatory volume decrease, RVD) cell volumes initially decreased to 81.5%; thereafter cell volumes increased to 90.8% of control. This post-RVD-RVI of 55.0% is also mediated by an increase in Na+ conductance. We conclude that rat hepatocytes in confluent primary culture are capable of RVI as well as of post-RVD-RVI. In this system, hypertonic stress leads to a considerable increase in cell membrane Na+ conductance. In concert with conductive Na+ influx, cell K+ is then increased via activation of Na+/K(+)-ATPase. An additional role of Na+/H+ exchange in the volume regulation of rat hepatocytes remains to be defined.

Secondary regulatory volume increase conferred on Xenopus oocytes by expression of AE2 anion exchanger

1997 ◽  
Vol 272 (1) ◽  
pp. C191-C202 ◽  
Author(s):  
L. Jiang ◽  
M. N. Chernova ◽  
S. L. Alper
Keyword(s):  
Volume Regulation ◽  
Xenopus Oocytes ◽  
Disulfonic Acid ◽  
Functional Coupling ◽  
Intrinsic Volume ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Hypertonic Stimulation ◽  
Shrinkage Prior ◽  
Hypotonic Swelling

Xenopus oocytes lack volume regulation and Cl/anion-exchange (AE) activity but express endogenous Na+/H+ exchange (NHE). We postulated that expression in oocytes of heterologous anion exchangers might allow regulatory volume increase (RVI) via functional coupling with endogenous NHE. Expression of neither erythroid nor kidney isoforms of AE1 conferred any form of RVI. In contrast, although AE2 expression did not confer primary RVI, it did confer on oocytes secondary RVI, with a requirement for hypotonic swelling before hypertonic shrinkage. This secondary RVI required extracellular Cl- and Na+, was blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and amiloride, was bumetanide insensitive, and was blocked by prevention of intracellular alkalinization, all properties consistent with functional coupling of AE2-mediated Cl-/HCO3- exchange and endogenous NHE. RVI was unaffected by CO2-HCO3- or by partial oocyte Cl- depletion and was unrelated to the rate of oocyte shrinkage. Prior hypotonic swelling did not significantly alter subsequent hypertonic stimulation of AE2-mediated 36Cl influx or efflux. We conclude that heterologous AE2 expression suffices to confer volume regulation on Xenopus oocytes that lack intrinsic volume-regulatory mechanisms.

scholarly journals Pressure- and Temperature-Induced Insertion of N2, O2 and CH4 to Ag-Natrolite

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4096
Author(s):  
Donghoon Seoung ◽  
Hyeonsu Kim ◽  
Pyosang Kim ◽  
Yongmoon Lee
Keyword(s):  
Unit Cell Volume ◽  
Molecular Size ◽  
Unit Cell ◽  
Volume Changes ◽  
Volume Increase ◽  
X Ray ◽  
Onset Pressure ◽  
Two Stages ◽  
Cell Volumes

This paper aimed to investigate the structural and chemical changes of Ag-natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) in the presence of different pressure transmitting mediums (PTMs), such as N2, O2 and CH4, up to ~8 GPa and 250 °C using in situ synchrotron X-ray powder diffraction and Rietveld refinement. Pressure-induced insertion occurs in two stages in the case of N2 and O2 runs, as opposed to the CH4 run. First changes of the unit cell volume in N2, O2 and CH4 runs are observed at 0.88(5) GPa, 1.05(5) GPa and 1.84(5) GPa with increase of 5.7(1)%, 5.5(1)% and 5.7(1)%, respectively. Subsequent volume changes of Ag-natrolite in the presence of N2 and O2 appear at 2.15(5) GPa and 5.24(5) GPa with a volume increase of 0.8(1)% and a decrease of 3.0(1)%, respectively. The bulk moduli of the Ag-NAT change from 42(1) to 49(7), from 38(1) to 227(1) and from 49(3) to 79(2) in the case of N2, O2 and CH4 runs, respectively, revealing that the Ag-NAT becomes more incompressible after each insertion of PTM molecules. The shape of the channel window of the Ag-NAT changes from elliptical to more circular after the uptake of N2, O2 and CH4. Overall, the experimental results of Ag-NAT from our previous data and this work establish that the onset pressure exponentially increases with the molecular size. The unit cell volumes of the expanded (or contracted) phases of the Ag-NAT have a linear relationship and limit to maximally expand and contract upon pressure-induced insertion.

scholarly journals Extracellular Vesicles Mediate Anti-Oxidative Response—In Vitro Study in the Ocular Drainage System

2020 ◽  
Vol 21 (17) ◽  
pp. 6105 ◽  
Author(s):  
Natalie Lerner ◽  
Itay Chen ◽  
Sofia Schreiber-Avissar ◽  
Elie Beit-Yannai
Keyword(s):  
Extracellular Vesicles ◽  
Aqueous Humor ◽  
Open Angle Glaucoma ◽  
Drainage System ◽  
In Vitro Study ◽  
Ciliary Epithelium ◽  
Target Cells ◽  
Related Factor ◽  
Antioxidant Genes

The importance of extracellular vesicles (EVs) as signaling mediators has been emphasized for several pathways with only limited data regarding their role as protective messages during oxidative stress (OS). The ocular drainage system is unique by being continuously exposed to OS and having a one-way flow of the aqueous humor carrying EVs taking role in glaucoma disease. Here, we aimed to examine the ability of EVs derived from the non-pigmented ciliary epithelium (NPCE)—the aqueous humor producing cells exposed to OS—to deliver protecting messages to the trabecular meshwork (TM)—the aqueous humor draining cells—a process with significance to the pathophysiology of glaucoma disease. EVs extracted from media of NPCE cells exposed to non-lethal OS and their unstressed control were incubated with TM cells. The effects of EVs derived from oxidative stressed cells on the activation of the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 (Nrf2-Keap1), a major OS pathway, and of the Wnt pathway, known for its role in primary open-angle glaucoma, were evaluated. EVs derived from oxidized NPCE cells significantly protected TM cells from direct OS. The TM cells uptake of EVs from oxidized NPCE and their cytosolic Nrf2 levels were significantly higher at 8 h post-exposure. EVs derived from oxidized NPCE cells significantly attenuated Wnt protein expression in TM cells and activated major antioxidant genes as measured by qRT-PCR. TM cells exposed to EVs derived from oxidized NPCE cells exhibited significantly lower OS and higher super oxide dismutase and catalase activity. Finally, we were able to show that carbonylated proteins and products of oxidized protein are presented in significantly higher levels in EVs derived from oxidized NPCE cells, supporting their suggested role in the signaling process. We hypothesize that these findings may have implications beyond understanding the pathophysiology of glaucoma disease and that transmitting signals that activate the antioxidant system in target cells represent a broad response common to many tissues communication.

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