title: Ca2+ channels in retinal pigment epithelial cells regulate vascular endothelial growth factor secretion rates in health and disease.
abstract: OBJECTIVE
  Choroidal neovascularization (CNV) is the most severe complication in age-related macular degeneration. The major angiogenic factor involved is vascular endothelial growth factor (VEGF) secreted by the retinal pigment epithelium (RPE). Since RPE cells express neuroendocrine L-type Ca2+ channels we investigated their involvement in VEGF secretion in normal RPE cells and RPE cells from patients with CNV.
  
  
  METHODS
  Freshly isolated and cultured RPE cells were studied using the patch-clamp technique and ELISA-based secretion assays.
  
  
  RESULTS
  Both freshly isolated and cultured cells showed whole-cell Ba2+ currents with properties of L-type Ca2+ currents: high activation threshold, sensitivity to dihydropyridines (10 muM nifedipine) and slow inactivation. VEGF-A secretion was elevated by BayK8644 (10 microM) or basic fibroblast growth factor (bFGF, 10 ng/ml), both of which are able to activate L-type channels. Cells from CNV tissue also showed nifedipine-sensitive Ba2+ currents, which displayed a voltage-dependent activation at more negative potentials, faster inactivation and changed regulation by tyrosine kinase pp60(c-src). The CNV RPE cells showed higher VEGF secretion rates which were reduced by nifedipine.
  
  
  CONCLUSIONS
  Thus, L-type Ca2+ channels in normal RPE cells regulate the secretion of VEGF. RPE cells from eyes with CNV maintain a VEGF secretion regulated by nifedipine-sensitve Ca2+ channels which might be of importance for the development of CNV.
authors.affiliation: Institut für Klinische Physiologie, Charité-Universitatsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Rosenthal
authors.forename: Heinrich
authors.initials: H
authors.lastname: Heimann
authors.forename: Hansjürgen
authors.initials: H
authors.lastname: Agostini
authors.forename: Gottfried
authors.initials: G
authors.lastname: Martin
authors.forename: Lutz Lothar
authors.initials: LL
authors.lastname: Hansen
authors.forename: Olaf
authors.initials: O
authors.lastname: Strauss
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000368:Aged; D001464:Barium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D020256:Choroidal Neovascularization / Q000378:metabolism*; D004553:Electric Conductivity; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006262:Health; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002120:Calcium Channel Agonists; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D007473:Ion Channels; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D016392:Proto-Oncogene Proteins pp60(c-src); D009543:Nifedipine