Endothelin receptor A is expressed and mediates the [Ca2+]i mobilization of cells in human ciliary smooth muscle, ciliary nonpigmented epithelium, and trabecular meshwork

Tao, Wenhong; Prasanna, Ganesh; Dimitrijevich, Slobodan D.; Yorio, Thomas

doi:10.1076/ceyr.17.1.31.5256

Cited by 39 publications

(24 citation statements)

References 10 publications

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“…Elevation of hydraulic pressure also induced a rise in cytosolic calcium [108], in accordance with the observation that trabecular facility decreases with rising intraocular pressure [1, 96]. Endothelin 1 and histamine [38, 101, 102, 109]also elevated internal calcium in trabecular meshwork, while angiotensin II had no effect [102]. …”

Section: Intracellular Calciumsupporting

confidence: 56%

Regulation of Trabecular Meshwork Contractility

Stumpff

Wiederholt²

2000

Ophthalmologica

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Ample evidence supports the theory that trabecular meshwork possesses smooth-muscle-like properties. Trabecular meshwork cells express a large number of transporters, channels and receptors, many of which are known to regulate smooth-muscle contractility. It has been shown that trabecular meshwork can be induced to contract and relax in response to pharmacological agents. In the model of the bovine eye, confirmed in some cases by experiments on primates, agents that contract trabecular meshwork reduce outflow. On the cellular level, this is coupled with depolarization and a rise in intracellular calcium. Relaxation of trabecular meshwork, on the other hand, appears to be coupled to a stimulation of the maxi-K channel, inducing hyperpolarization and a closure of L-type calcium channels. No significant differences between cells from a human and a bovine source emerged, either in classical measurements of membrane voltage, in measurements of intracellular calcium or patch-clamp experiments. Thus, pharmacological agents that relax trabecular meshwork seem promising candidates for further research – the ultimate goal being an improvement of glaucoma therapy in humans.

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Section: Intracellular Calciumsupporting

confidence: 56%

Regulation of Trabecular Meshwork Contractility

Stumpff

Wiederholt²

2000

Ophthalmologica

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“…In bovine eyes, an ET-1-induced TM contraction was also observed [15]; it was also suggested that ET-1 may be involved in the regulation of aqueous humour dynamics by changing [Ca 2+ ] i and intracellular pH [25,26] in TM cells.…”

Section: Resultsmentioning

confidence: 99%

Effects of Endothelin-1 on Human Trabecular Meshwork Cell Contraction

Cellini¹,

Versura²,

Trerè

et al. 2005

Ophthalmic Res

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Trabecular meshwork (TM) cells are now considered to play an active role in the aqueous outflow mechanism, since they exhibit smooth muscle-like contractile properties. Endothelin-1 (ET-1), a potent vasoconstrictor peptide, has been proposed to play a role in the local regulation of aqueous outflow and intra-ocular pressure control. We propose an in vitro culture model as a method in the study of ET-1-induced human trabecular meshwork (HTM) cell contractility. Experiments were performed on semi-confluent HTM cells (primary cultures established from normotensive human donor eyes) at the 2nd passage with PBS as control, ET-1, sarafotoxin 6c (a selective endothelin B receptor agonist) and Y-27632 (a selective inhibitor of rho-associated kinase). The contractile status of the cells was evaluated by a morphometric analysis of the cell area, assuming that HTM cells in culture are able to reduce their area as a consequence of cytoskeletal contraction rather than regulatory volume decrease. Our data indicate that image analysis of the HTM cell area can be a reliable method in the study of TM cell contractility, since it utilizes human cells and offers versatile opportunities for the pharmacological evaluation of drugs controlling HTM cell status.

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“…Following this, several investigators were able to isolate the ciliary body epithelia of toad, shark, rabbit, and bovine with which active transport mechanisms for Cl -, Na + and HCO 3 -were described . Complementing this work, other investigators have used the isolated tissue to look for transporters with intracellular electrodes (Chu and Green, 1990;Wiederholt and Zadunaisky, 1986), fluorescent probes (Butler et al, 1994;Wolosin et al, 1991), electron probe (Bowler et al, 1996;Macknight et al, 2000), and patch clamp techniques (Chen and Sears, 1997;Chen et al, 1998;Edelman et al,1995;Wang et al, 2000), or have used cultured CE cells to look for channels using microelectrodes (Helbig et al, 1989c) or patch-clamping CoCa-Prados et al,1995,1996Yantorno et al, 1992), and for transporters using radioisotopes (Helbig et al 1988(Helbig et al ,1989a(Helbig et al ,1989b, or fluorescent techniques (Tao et al, 1998;Hou et al, 1998Hou et al, ,2000. As a result of this wealth of information, several models have been proposed to explain aqueous humor production by the ciliary epithelium (Civan, 1997;Civan and Macknight, 2004;Jacob and Civan, 1996).…”

Section: Fluid and Electrolyte Transport Studies On Isolated Ciliary mentioning

confidence: 99%

Fluid transport phenomena in ocular epithelia

Candia

Alvarez

2008

Progress in Retinal and Eye Research

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This article discusses three largely unrecognized aspects related to fluid movement in ocular tissues; namely, a) the dynamic changes in water permeability observed in corneal and conjunctival epithelia under anisotonic conditions; b) the indications that the fluid transport rate exhibited by the ciliary epithelium is insufficient to explain aqueous humor production; and c) the evidence for fluid movement into and out of the lens during accommodation. We have studied each of these subjects in recent years and present an evaluation of our data within the context of the results of others who have also worked on electrolyte and fluid transport in ocular tissues. We propose that 1) the corneal and conjunctival epithelia, with apical aspects naturally exposed to variable tonicities, are capable of regulating their water permeabilities as part of the cell-volume regulatory process, 2) fluid may directly enter the anterior chamber of the eye across the anterior surface of the iris, thereby representing an additional entry pathway for aqueous humor production, and 3) changes in lens volume occur during accommodation, and such changes are best explained by a net influx and efflux of fluid.

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Endothelin receptor A is expressed and mediates the [Ca2+]i mobilization of cells in human ciliary smooth muscle, ciliary nonpigmented epithelium, and trabecular meshwork

Abstract: ETA receptor is expressed and is possibly responsible for mediating the signal for [Ca2+]i mobilization by ET-1 in human ciliary smooth muscle, ciliary nonpigmented epithelial cells, and trabecular meshwork cells.

Cited by 39 publications

References 10 publications

Regulation of Trabecular Meshwork Contractility

Regulation of Trabecular Meshwork Contractility

Effects of Endothelin-1 on Human Trabecular Meshwork Cell Contraction

Fluid transport phenomena in ocular epithelia

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