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J Membr Biol. 2001 Sep 15;183(2):93-101.

Cell signaling pathways mediating epidermal growth factor stimulation of Na:K:2Cl cotransport activity in rabbit corneal epithelial cells.

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College of Optometry, Department of Biological Sciences, State University of New York, 33 W. 42nd Street, New York, NY 10036, USA.


We characterized the signaling and ion transport pathways that mediate epidermal growth factor receptor physiological control in SV40-immortalized rabbit corneal epithelial cells (tRCEC). Our evaluation employed single-cell fluorescence imaging to measure the intracellular [Na+]i in these cells loaded with the Na+ sensitive dye, SBFI. EGF (1 to 5 ng/ml) transiently increased [Na+]i from 10 mm to as much as 35 mm after 25 min, which was followed by a decline towards its control value. These increases waned at higher EGF concentrations up to 50 ng/ml. Both inhibition of EGF receptor-linked tyrosine kinase activity (50 microm RG-13022) and cPLA2 activity (10 microm AACOCF3) obviated EGF-induced increases in [Na+]i. In contrast, PGE2 (10 microg/ml) and cAMP (2 mm) increased [Na+]i by 25 mm. Inhibition of NKCC activity through exposure to either Cl-free Ringers or 300 microm furosemide in NaCl Ringers eliminated EGF-induced increases in [Na+]i. Similarly, EGF failed to increase [Na+]i following inhibition of: 1) PKA activity (10 microm H-89); 2) Erk1/2 (15 microm PD98059) or 3) p38 (15 microm SB203580) activity. Stimulation protein kinase C activity (0.1 microm PMA) transiently increased [Na+]i followed by a decline towards its baseline value. EGF-induced increases in [Na+]i were unaltered by inhibition of K+ conductance (100 microm 4-AP). Taken together, EGF stimulates Erk1/2; p38 and cPLA2 activity. Their stimulation increases PGE2 and cAMP levels resulting in PKA and NKCC activation.

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