Calcium influx induced by activation of receptor tyrosine kinases in SV40-transfected human corneal endothelial cells.

This study was undertaken to investigate electrophysiological properties of immortalized SV40-transfected human corneal endothelial cells (HCEC-SV40) combined with the analysis of intracellular Ca(2+) responses mediated by ligands for receptor tyrosine kinases (RTK). In addition, the effects of several tyrosine kinase inhibitors were tested on Ca(2+) inflow mediated by induction of capacitative calcium entry (CCE). Patch-clamp techniques and measurements of the intracellular free Ca(2+) ([Ca(2+)](i)) by fura-2 were performed using HCEC-SV40. Stimulation of fibroblast growth factor receptors (FGFR) (e.g. by basic-FGF) (10 ng ml(-1)) elicited activation of Ca(2+) permeable channels and a subsequent increase of cytosolic free Ca(2+) in HCEC-SV40. This effect could be disrupted by the L-type Ca(2+) channel blocker nifedipine (5 microM). In addition, nifedipine significantly reduced the magnitude of CCE. Inhibition of protein tyrosine kinases (PTKs) by genistein, lavendustin A, or tyrphostin 51 (all 5 microM) also led to a reduction of CCE in HCEC-SV40. This study demonstrates for the first time that L-type Ca(2+) channel activity in HCEC-SV40 is linked to the activity of FGF receptor tyrosine kinases. These data regarding Ca(2+) inflow through Ca(2+) channels could be useful for investigation of culture and vitality conditions of HCEC.