Na-K-Cl cotransport in normal and glaucomatous human trabecular meshwork cells

Research output: Contribution to journalArticle

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Abstract

PURPOSE. Previous results from this laboratory showed that intracellular volume of trabecular meshwork (TM) cells is regulated by the Na-K-Cl cotransport system. Other studies suggest that TM cell volume, in turn, is a determinant of permeability across the TM. Given that a decrease in outflow facility across the TM is thought to be the primary cause of elevated intraocular pressure in primary open-angle glaucoma, the present study was conducted to investigate the possibility that Na-K-Cl cotransport function may be altered in glaucomatous TM cells compared with normal TM cells. METHODS. Normal and glaucomatous human TM cells were cultured from donor eyes and trabeculectomy specimens, respectively. Trabecular meshwork cell monolayers were evaluated for Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx using 86Rb as a tracer for K. Cotransporter protein expression was determined by western blot analysis, and intracellular volume was determined radioisotopically using [14C]urea and [14C]sucrose as markers of total and extracellular water space, respectively. RESULT. Na-K-Cl cotransport activity of glaucomatous TM cells was found to be reduced by 32% ± 2% compared with that of normal TM cells, whereas western blot analyses showed that cotransporter protein expression in glaucomatous TM cells was reduced by 64% ± 14% compared with expression in normal TM cells. Also, exposure of normal TM cells to 10 μM norepinephrine or 50 μM 8-bromo-3',5'-cyclic adenosine monophosphate was found to diminish Na-K-Cl cotransport activity, whereas these agents were without effect on glaucomatous TM cell cotransport. Finally, resting cell volume of glaucomatous TM cells was found to be increased compared with that of normal TM cells, whereas intracellular volume of both cell types was reduced after exposure to 10 μM benzmetanide or 10 μM bumetanide. CONCLUSIONS. These findings indicate that Na-K-Cl cotransport function and regulation are altered in glaucomatous TM cells compared with that of normal TM cells. However, the observation that cell volume of glaucomatous TM cells is greater than that of normal TM cells, despite reduced Na-K-Cl cotransport activity, suggests that other volume-regulatory ion flux pathways may be involved in the reduced outflow of glaucoma.

Original languageEnglish (US)
Pages (from-to)425-434
Number of pages10
JournalInvestigative Ophthalmology and Visual Science
Volume40
Issue number2
StatePublished - Feb 1999

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Trabecular Meshwork
Cell Size
Bumetanide
Western Blotting

ASJC Scopus subject areas

  • Ophthalmology

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Na-K-Cl cotransport in normal and glaucomatous human trabecular meshwork cells. / Putney, Luanna K.; Brandt, James D; O'Donnell, Martha E.

In: Investigative Ophthalmology and Visual Science, Vol. 40, No. 2, 02.1999, p. 425-434.

Research output: Contribution to journalArticle

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title = "Na-K-Cl cotransport in normal and glaucomatous human trabecular meshwork cells",
abstract = "PURPOSE. Previous results from this laboratory showed that intracellular volume of trabecular meshwork (TM) cells is regulated by the Na-K-Cl cotransport system. Other studies suggest that TM cell volume, in turn, is a determinant of permeability across the TM. Given that a decrease in outflow facility across the TM is thought to be the primary cause of elevated intraocular pressure in primary open-angle glaucoma, the present study was conducted to investigate the possibility that Na-K-Cl cotransport function may be altered in glaucomatous TM cells compared with normal TM cells. METHODS. Normal and glaucomatous human TM cells were cultured from donor eyes and trabeculectomy specimens, respectively. Trabecular meshwork cell monolayers were evaluated for Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx using 86Rb as a tracer for K. Cotransporter protein expression was determined by western blot analysis, and intracellular volume was determined radioisotopically using [14C]urea and [14C]sucrose as markers of total and extracellular water space, respectively. RESULT. Na-K-Cl cotransport activity of glaucomatous TM cells was found to be reduced by 32{\%} ± 2{\%} compared with that of normal TM cells, whereas western blot analyses showed that cotransporter protein expression in glaucomatous TM cells was reduced by 64{\%} ± 14{\%} compared with expression in normal TM cells. Also, exposure of normal TM cells to 10 μM norepinephrine or 50 μM 8-bromo-3',5'-cyclic adenosine monophosphate was found to diminish Na-K-Cl cotransport activity, whereas these agents were without effect on glaucomatous TM cell cotransport. Finally, resting cell volume of glaucomatous TM cells was found to be increased compared with that of normal TM cells, whereas intracellular volume of both cell types was reduced after exposure to 10 μM benzmetanide or 10 μM bumetanide. CONCLUSIONS. These findings indicate that Na-K-Cl cotransport function and regulation are altered in glaucomatous TM cells compared with that of normal TM cells. However, the observation that cell volume of glaucomatous TM cells is greater than that of normal TM cells, despite reduced Na-K-Cl cotransport activity, suggests that other volume-regulatory ion flux pathways may be involved in the reduced outflow of glaucoma.",
author = "Putney, {Luanna K.} and Brandt, {James D} and O'Donnell, {Martha E}",
year = "1999",
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T1 - Na-K-Cl cotransport in normal and glaucomatous human trabecular meshwork cells

AU - Putney, Luanna K.

AU - Brandt, James D

AU - O'Donnell, Martha E

PY - 1999/2

Y1 - 1999/2

N2 - PURPOSE. Previous results from this laboratory showed that intracellular volume of trabecular meshwork (TM) cells is regulated by the Na-K-Cl cotransport system. Other studies suggest that TM cell volume, in turn, is a determinant of permeability across the TM. Given that a decrease in outflow facility across the TM is thought to be the primary cause of elevated intraocular pressure in primary open-angle glaucoma, the present study was conducted to investigate the possibility that Na-K-Cl cotransport function may be altered in glaucomatous TM cells compared with normal TM cells. METHODS. Normal and glaucomatous human TM cells were cultured from donor eyes and trabeculectomy specimens, respectively. Trabecular meshwork cell monolayers were evaluated for Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx using 86Rb as a tracer for K. Cotransporter protein expression was determined by western blot analysis, and intracellular volume was determined radioisotopically using [14C]urea and [14C]sucrose as markers of total and extracellular water space, respectively. RESULT. Na-K-Cl cotransport activity of glaucomatous TM cells was found to be reduced by 32% ± 2% compared with that of normal TM cells, whereas western blot analyses showed that cotransporter protein expression in glaucomatous TM cells was reduced by 64% ± 14% compared with expression in normal TM cells. Also, exposure of normal TM cells to 10 μM norepinephrine or 50 μM 8-bromo-3',5'-cyclic adenosine monophosphate was found to diminish Na-K-Cl cotransport activity, whereas these agents were without effect on glaucomatous TM cell cotransport. Finally, resting cell volume of glaucomatous TM cells was found to be increased compared with that of normal TM cells, whereas intracellular volume of both cell types was reduced after exposure to 10 μM benzmetanide or 10 μM bumetanide. CONCLUSIONS. These findings indicate that Na-K-Cl cotransport function and regulation are altered in glaucomatous TM cells compared with that of normal TM cells. However, the observation that cell volume of glaucomatous TM cells is greater than that of normal TM cells, despite reduced Na-K-Cl cotransport activity, suggests that other volume-regulatory ion flux pathways may be involved in the reduced outflow of glaucoma.

AB - PURPOSE. Previous results from this laboratory showed that intracellular volume of trabecular meshwork (TM) cells is regulated by the Na-K-Cl cotransport system. Other studies suggest that TM cell volume, in turn, is a determinant of permeability across the TM. Given that a decrease in outflow facility across the TM is thought to be the primary cause of elevated intraocular pressure in primary open-angle glaucoma, the present study was conducted to investigate the possibility that Na-K-Cl cotransport function may be altered in glaucomatous TM cells compared with normal TM cells. METHODS. Normal and glaucomatous human TM cells were cultured from donor eyes and trabeculectomy specimens, respectively. Trabecular meshwork cell monolayers were evaluated for Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx using 86Rb as a tracer for K. Cotransporter protein expression was determined by western blot analysis, and intracellular volume was determined radioisotopically using [14C]urea and [14C]sucrose as markers of total and extracellular water space, respectively. RESULT. Na-K-Cl cotransport activity of glaucomatous TM cells was found to be reduced by 32% ± 2% compared with that of normal TM cells, whereas western blot analyses showed that cotransporter protein expression in glaucomatous TM cells was reduced by 64% ± 14% compared with expression in normal TM cells. Also, exposure of normal TM cells to 10 μM norepinephrine or 50 μM 8-bromo-3',5'-cyclic adenosine monophosphate was found to diminish Na-K-Cl cotransport activity, whereas these agents were without effect on glaucomatous TM cell cotransport. Finally, resting cell volume of glaucomatous TM cells was found to be increased compared with that of normal TM cells, whereas intracellular volume of both cell types was reduced after exposure to 10 μM benzmetanide or 10 μM bumetanide. CONCLUSIONS. These findings indicate that Na-K-Cl cotransport function and regulation are altered in glaucomatous TM cells compared with that of normal TM cells. However, the observation that cell volume of glaucomatous TM cells is greater than that of normal TM cells, despite reduced Na-K-Cl cotransport activity, suggests that other volume-regulatory ion flux pathways may be involved in the reduced outflow of glaucoma.

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JO - Investigative Ophthalmology and Visual Science

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