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S Mergler, H Dannowski, J Bednarz, K Engelmann, C Hartmann, U Pleyer; Electrophysiological Properties in Cultured Human Corneal Endothelial Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3183.
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Purpose: The aim of this study was to characterize electrophysiological properties of SV40-immortalized human corneal endothelial cells (HCE-SV40) as well as to describe intracellular Ca2+ responses mediated by ligands for protein tyrosine kinases (PTKs) coupled receptors such as fibroblast growth factor receptor 1 (FGFR1). In addition, the effect of several tyrosine kinase inhibitors was tested on Ca2+ influx mediated by induction of capacitative Ca2+ entry (CCE). Methods: The electrophysiological studies were performed by patch-clamp techniques combined with the fluorimetric measuring method by Grynkiewicz et al., 1985, J. Biol. Chem. 260: 3440-3450. Results: HCE-SV40 cells express voltage-operated Ca2+ channels (VOCCs) similar to L-type channels observed in rabbit corneal epithelial cells (Rich and Rae, 1995, J. Membr. Biol.144: 177-184) but likely in a minor portion of the whole Ca2+ channel conductance. Application of acidic FGF (10 ng/ml) led to an activation of Ca2+ permeable channels and a subsequent increase of cytosolic free Ca2+. Inversely, the magnitude of CCE was reduced by the L-type channel blocker nifedipine (5 µM) from 527 ± 78 nM (n = 10) (without drug) to 244 ± 16 nM (n = 15). Intriguingly, PTK inhibitors, such as lavendustin A and tyrphostin 51 (both 5 µM) did reduce CCE magnitude at significant higher levels (145 ± 26 nM; n = 6 and 218 ± 31 nM; n = 8). Conclusion: We could demonstrate for the first time that not only L-type Ca2+ channel activity but also a putative non-voltage-dependent Ca2+ permeable channel pathway affected by tyrosine kinase inhibitors is present in permanent HCE-SV40 cells. Moreover, the prevailing tyrosine kinase-sensitive non-voltage dependent Ca2+ permeable channel activity could be presumably associated with a high density of FGF receptor tyrosine kinases, such as FGFR1 expressed in HCE-SV40 cells. CR: none
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