Calcium influx induced by activation of tyrosine kinase receptors in cultured bovine aortic endothelial cells
✍ Scribed by Luca Munaron; Alessandra Fiorio Pla
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 220 KB
- Volume
- 185
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
We studied the ionic currents activated by basic fibroblast growth factor (bFGF) and insulin-like growth factor-I (IGF-I) in cultured bovine aortic endothelial cells (BAE-1) by using patch-clamp and single-cell fluorimetric calcium measurements. In whole-cell, voltage-clamp experiments at V h ϭ Ϫ50 mV, the addition of either bFGF (20 ng/ml) or IGF-I (50 ng/ml) induced an inward current with similar amplitude, time course, and permeation properties. The response was dependent on receptor occupancy and showed a desensitisation in the continued presence of the factors. Ionic substitutions in whole-cell experiments indicated that the current barely discriminated among Na ϩ , Ca ϩ , and K ϩ ions. Accordingly, stimulation with bFGF or IGF-I induced a dose-dependent [Ca 2ϩ ] i elevation completely due to entry from the extracellular medium, whereas no detectable release from internal stores was observed. Calcium influx was dependent on protein tyrosine kinase (PTK) activity; it was significantly inhibited by treatment with genistein or tyrphostin 47, two PTK inhibitors, and not affected by inactive analogues, daidzein, and tyrphostin 1. Moreover, addition of 200 M Na 3 VO 4 , an inhibitor of protein tyrosine phosphatase (PTP) activity, evoked the responses to the factors both in patch-clamp and in fluorimetric measurements. Cellattached recordings using 100 mM CaCl 2 in the pipette showed that bFGF and IGF-I activate calcium-permeable channels with similar properties. These results provide evidence for a calcium influx induced by two factors that bind to tyrosine kinase receptors (RTK) in endothelial cells.