Abstract
The trabecular meshwork (TM) of the eye plays a central role in modulating intraocular pressure by regulating aqueous humor outflow, although the mechanisms are largely unknown. We and others have shown previously that aqueous humor outflow facility is modulated by conditions that alter TM cell volume. We have also shown that the Na-K-Cl cotransport system is a primary regulator of TM cell volume and that its activity appears to be coordinated with net efflux pathways to maintain steady-state volume. However, the cellular mechanisms that regulate cotransport activity and cell volume in TM cells have yet to be elucidated. The present study was conducted to investigate the hypothesis that intracellular Cl concentration ([Cl](i)) acts to regulate TM cell Na-K-Cl cotransport activity, as has been shown previously for some other cell types. We demonstrate here that the human TM cell Na-K-Cl cotransporter is highly sensitive to changes in [Cl](i). Our findings reveal a marked stimulation of Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx, in TM cells following preincubation of cells with Cl-free medium as a means of reducing [Cl](i). In contrast, preincubation of cells with media containing elevated K concentrations as a means of increasing [Cl](i) results in inhibition of Na- K-Cl cotransport activity. The effects of reducing [Cl](i), as well as elevating [Cl](i), on Na-K-Cl cotransport activity are concentration dependent. Furthermore, the stimulatory effect of reduced [Cl](i) is additive with cell-shrinkage-induced stimulation of the cotransporter. Our studies also show that TM cell Na-K-Cl cotransport activity is altered by a variety of Cl channel modulators, presumably through changes in [Cl](i). These findings support the hypothesis that regulation of Na-K-Cl cotransport activity, and thus cell volume, by [Cl](i) may participate in modulating outflow facility across the TM.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Cell Physiology |
| Volume | 277 |
| Issue number | 3 46-3 |
| State | Published - 1999 |
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Keywords
- Aqueous outflow
- Chloride channel
- Glaucoma
- Intracellular volume
- Niflumic acid
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology
- Physiology
- Physiology (medical)
Cite this
Intracellular Cl regulates Na-K-Cl cotransport activity in human trabecular meshwork cells. / Putney, Luanna K.; Vibat, Cecile Rose T; O'Donnell, Martha E.
In: American Journal of Physiology - Cell Physiology, Vol. 277, No. 3 46-3, 1999.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Intracellular Cl regulates Na-K-Cl cotransport activity in human trabecular meshwork cells
AU - Putney, Luanna K.
AU - Vibat, Cecile Rose T
AU - O'Donnell, Martha E
PY - 1999
Y1 - 1999
N2 - The trabecular meshwork (TM) of the eye plays a central role in modulating intraocular pressure by regulating aqueous humor outflow, although the mechanisms are largely unknown. We and others have shown previously that aqueous humor outflow facility is modulated by conditions that alter TM cell volume. We have also shown that the Na-K-Cl cotransport system is a primary regulator of TM cell volume and that its activity appears to be coordinated with net efflux pathways to maintain steady-state volume. However, the cellular mechanisms that regulate cotransport activity and cell volume in TM cells have yet to be elucidated. The present study was conducted to investigate the hypothesis that intracellular Cl concentration ([Cl](i)) acts to regulate TM cell Na-K-Cl cotransport activity, as has been shown previously for some other cell types. We demonstrate here that the human TM cell Na-K-Cl cotransporter is highly sensitive to changes in [Cl](i). Our findings reveal a marked stimulation of Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx, in TM cells following preincubation of cells with Cl-free medium as a means of reducing [Cl](i). In contrast, preincubation of cells with media containing elevated K concentrations as a means of increasing [Cl](i) results in inhibition of Na- K-Cl cotransport activity. The effects of reducing [Cl](i), as well as elevating [Cl](i), on Na-K-Cl cotransport activity are concentration dependent. Furthermore, the stimulatory effect of reduced [Cl](i) is additive with cell-shrinkage-induced stimulation of the cotransporter. Our studies also show that TM cell Na-K-Cl cotransport activity is altered by a variety of Cl channel modulators, presumably through changes in [Cl](i). These findings support the hypothesis that regulation of Na-K-Cl cotransport activity, and thus cell volume, by [Cl](i) may participate in modulating outflow facility across the TM.
AB - The trabecular meshwork (TM) of the eye plays a central role in modulating intraocular pressure by regulating aqueous humor outflow, although the mechanisms are largely unknown. We and others have shown previously that aqueous humor outflow facility is modulated by conditions that alter TM cell volume. We have also shown that the Na-K-Cl cotransport system is a primary regulator of TM cell volume and that its activity appears to be coordinated with net efflux pathways to maintain steady-state volume. However, the cellular mechanisms that regulate cotransport activity and cell volume in TM cells have yet to be elucidated. The present study was conducted to investigate the hypothesis that intracellular Cl concentration ([Cl](i)) acts to regulate TM cell Na-K-Cl cotransport activity, as has been shown previously for some other cell types. We demonstrate here that the human TM cell Na-K-Cl cotransporter is highly sensitive to changes in [Cl](i). Our findings reveal a marked stimulation of Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx, in TM cells following preincubation of cells with Cl-free medium as a means of reducing [Cl](i). In contrast, preincubation of cells with media containing elevated K concentrations as a means of increasing [Cl](i) results in inhibition of Na- K-Cl cotransport activity. The effects of reducing [Cl](i), as well as elevating [Cl](i), on Na-K-Cl cotransport activity are concentration dependent. Furthermore, the stimulatory effect of reduced [Cl](i) is additive with cell-shrinkage-induced stimulation of the cotransporter. Our studies also show that TM cell Na-K-Cl cotransport activity is altered by a variety of Cl channel modulators, presumably through changes in [Cl](i). These findings support the hypothesis that regulation of Na-K-Cl cotransport activity, and thus cell volume, by [Cl](i) may participate in modulating outflow facility across the TM.
KW - Aqueous outflow
KW - Chloride channel
KW - Glaucoma
KW - Intracellular volume
KW - Niflumic acid
UR - http://www.scopus.com/inward/record.url?scp=0032862115&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032862115&partnerID=8YFLogxK
M3 - Article
C2 - 10484324
AN - SCOPUS:0032862115
VL - 277
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 3 46-3
ER -