小梁网细胞体积调节中涉及的离子机制对房水流出的调节作用。

Modulation of aqueous humor outflow by ionic mechanisms involved in trabecular meshwork cell volume regulation.

作者信息

Soto David, Comes Núria, Ferrer Elisa, Morales Miguel, Escalada Artur, Palés Jordi, Solsona Carles, Gual Arcadi, Gasull Xavier

机构信息

Laboratory of Neurophysiology, Department of Physiological Sciences I-Institute of Biomedical Investigations August Pi i Sunyer, University of Barcelona, Spain.

出版信息

Invest Ophthalmol Vis Sci. 2004 Oct;45(10):3650-61. doi: 10.1167/iovs.04-0060.

DOI:10.1167/iovs.04-0060

PMID:15452073

Abstract

PURPOSE

Trabecular meshwork (TM) cell shape, volume, contractility and their interactions with extracellular matrix determine outflow facility. Because cell volume seems essential to TM function, this study was conducted to investigate further the ionic channels and receptors involved in regulatory volume decrease and their roles in modulating outflow facility.

METHODS

Primary cultures of bovine TM cells were used. K(+) and Cl(-) currents were studied with whole-cell patch clamping. Swelling was induced by hypotonic shock. Ca(2+) was measured in TM cells loaded with fura-2. Bovine anterior segments were perfused at constant pressure to measure outflow facility.

RESULTS

Hypotonic media activated both the high-conductance Ca(2+)-activated K(+) channel (BK(Ca)) and swelling-activated Cl(-) channel (Cl(swell)) currents and induced release of adenosine 5'-triphosphate (ATP) from TM cells. ATP activated P2Y(2) receptors with the following profile: ATP = uridine 5'-triphosphate (UTP) > adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma S) > adenosine 5'-diphosphate (ADP) = uridine 5'-diphosphate (UDP), and increased BK(Ca) current. Hypotonic medium initially decreased outflow facility in perfused anterior segments, which recovered with time to baseline levels. Addition of tamoxifen or iberiotoxin (Cl(swell) and BK(Ca) blockers, respectively) lengthened the recovery phase, which implies that these channels participate in cell volume regulation. In contrast, an activator of BK(Ca)s (NS1619) produced the opposite effect.

CONCLUSIONS

Cell swelling activates a regulatory volume decrease mechanism that implies activation of K(+) and Cl(-) currents and participation of P2Y(2) receptors. Because previous studies have shown that intracellular volume of TM cells is an important determinant of outflow facility, it seems feasible that cell volume regulation would be part of the homeostatic mechanisms of the TM, to regulate the outflow pathway.

摘要

目的

小梁网（TM）细胞的形状、体积、收缩性及其与细胞外基质的相互作用决定了房水流出易度。由于细胞体积似乎对TM功能至关重要，本研究旨在进一步探究参与调节性容积减小的离子通道和受体及其在调节房水流出易度中的作用。

方法

使用牛TM细胞的原代培养物。采用全细胞膜片钳技术研究钾离子（K⁺）和氯离子（Cl⁻）电流。通过低渗休克诱导细胞肿胀。使用负载fura-2的TM细胞测量细胞内钙离子浓度（[Ca²⁺]i）。对牛眼前节进行恒压灌注以测量房水流出易度。

结果

低渗培养基激活了高电导钙激活钾通道（BKCa）和肿胀激活氯通道（Clswell）电流，并诱导TM细胞释放三磷酸腺苷（ATP）。ATP以如下顺序激活P2Y2受体：ATP = 尿苷三磷酸（UTP）> 腺苷5'-O-(3-硫代三磷酸)（ATP-γS）> 腺苷二磷酸（ADP） = 尿苷二磷酸（UDP），并增加BKCa电流。低渗培养基最初会降低灌注眼前节的房水流出易度，随后随时间恢复至基线水平。添加他莫昔芬或iberiotoxin（分别为Clswell和BKCa阻滞剂）会延长恢复阶段，这表明这些通道参与细胞容积调节。相反，BKCa激活剂（NS1619）产生相反的效果。