Growth factor-induced cytosolic calcium ion transients in cultured human retinal pigment epithelial cells.
Growth factor-induced changes of cytosolic free calcium ion concentration ([Ca2+]i) and phosphatidylinositol (PI) turnover in cultured human retinal pigment epithelial (RPE) cells were studied, and their temporal relationship was compared. After a 24-hr serum depletion, RPE cells were loaded with fura-2/AM, and [Ca2+]i was analyzed using a digital imaging microscopy system. The resting [Ca2+]i in a single cultured human RPE cell was 153 +/- 1.5 nM (mean +/- the standard error of the mean [SEM], n = 105). The percentage of reactive cells that had Ca2+ transients induced by various growth factors were: epidermal growth factor, 18%; basic fibroblast growth factor (bFGF), 5%; nerve growth factor, 15%; platelet-derived growth factor (PDGF), 70%; insulin-like growth factor, 0%; fibronectin, 0%; insulin, 3%; and fetal bovine serum (FBS), 100%. The PDGF showed a peak concentration of 237 +/- 4.7 nM (mean +/- SEM, n = 67) and FBS, 774 +/- 34.5 nM (mean +/- SEM, n = 52). Chelation of the extracellular Ca2+ by EGTA made the resting and peak concentration lower. The Ca2+ transients occurred within 60 sec and lasted less than 5 min after the application of the growth factors. However, measurements of phosphoinositides in 24-hr serum-starved RPE cells revealed that growth factor-induced PI turnover was much slower than Ca2+ transients. In addition, FBS, bFGF, and PDGF increased the contents of inositol phosphate, inositol biphosphate, and inositol triphosphate (IP3) in RPE cells slowly up to 60 min except that PDGF showed a peak of IP3 at 15 min after stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Ophthalmology, Kyoto University Faculty of Medicine, Japan.
S
S
Kuriyama
T
T
Ohuchi
N
N
Yoshimura
Y
Y
Honda
D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002614:Chelating Agents; D003600:Cytosol / Q000378:metabolism*; D005333:Fetus; D016257:Fura-2 / Q000031:analogs & derivatives; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007295:Inositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects
D002614:Chelating Agents; D006133:Growth Substances; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; C049925:fura-2-am; D002118:Calcium; D016257:Fura-2