Adaptation by Corneal Epithelial Cells to Chronic Hypertonic Stress Depends on Upregulation of Na:K:2Cl Cotransporter Gene and Protein Expression and Ion Transport Activity

Adaptation by Corneal Epithelial Cells to Chronic Hypertonic Stress Depends on Upregulation of... We examined the ability of SV40-immortalized human and rabbit corneal epithelial cells (HCEC and RCEC, respectively) to adapt to chronic hypertonic stress. Under isotonic conditions, in the presence of 50 μm bumetanide, proliferation measured as 3H-thymidine incorporation declined in RCEC and HCEC by 8 and 35%, respectively. After 48 hr exposure to 375 mOsm medium, RCEC proliferation fell by 19% whereas in HCEC it declined by 45%. Light scattering behavior demonstrated that both cell lines mediate nearly complete regulatory volume increase (RVI) responses to an acute hypertonic (375 mOsm) challenge, which in part depend on bumetanide-sensitive Na-K-2Cl cotransporter (NKCC) activity. Following exposing RCEC for 48 hr to 375 mOsm medium, their RVI response to an acute hypertonic challenge was inhibited by 17%. However, in HCEC this response declined by 68%. During exposure to 375 mOsm medium for up to 24 hr, only RCEC upregulated NKCC gene and protein expression as well as bumetanide-sensitive 86Rb influx. These increases are consistent with the smaller declines in RVI and proliferation capacity occurring during this period in RCEC than in HCEC. Therefore, adaptation by RCEC to chronic hypertonic stress is dependent on stimulation of NKCC gene and protein expression and functional activity. On the other hand, under isotonic conditions, HCEC RVI and proliferation are more dependent on NKCC activity than they are in RCEC. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Adaptation by Corneal Epithelial Cells to Chronic Hypertonic Stress Depends on Upregulation of Na:K:2Cl Cotransporter Gene and Protein Expression and Ion Transport Activity

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2000 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002320001098
Publisher site
See Article on Publisher Site

Abstract

We examined the ability of SV40-immortalized human and rabbit corneal epithelial cells (HCEC and RCEC, respectively) to adapt to chronic hypertonic stress. Under isotonic conditions, in the presence of 50 μm bumetanide, proliferation measured as 3H-thymidine incorporation declined in RCEC and HCEC by 8 and 35%, respectively. After 48 hr exposure to 375 mOsm medium, RCEC proliferation fell by 19% whereas in HCEC it declined by 45%. Light scattering behavior demonstrated that both cell lines mediate nearly complete regulatory volume increase (RVI) responses to an acute hypertonic (375 mOsm) challenge, which in part depend on bumetanide-sensitive Na-K-2Cl cotransporter (NKCC) activity. Following exposing RCEC for 48 hr to 375 mOsm medium, their RVI response to an acute hypertonic challenge was inhibited by 17%. However, in HCEC this response declined by 68%. During exposure to 375 mOsm medium for up to 24 hr, only RCEC upregulated NKCC gene and protein expression as well as bumetanide-sensitive 86Rb influx. These increases are consistent with the smaller declines in RVI and proliferation capacity occurring during this period in RCEC than in HCEC. Therefore, adaptation by RCEC to chronic hypertonic stress is dependent on stimulation of NKCC gene and protein expression and functional activity. On the other hand, under isotonic conditions, HCEC RVI and proliferation are more dependent on NKCC activity than they are in RCEC.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Sep 1, 2000

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