| Abstract: | Confocal fluorescence microscopy was used to study the bradykinin-induced calcium signals in the neuro-blastoma × glioma cell line NG 108–15. We found that bradykinin induced a rise in free calcium, not only in the cytoplasm but also in the nucleus. The nuclear and cytosolic calcium concentrations were not significantly different and rose to about 1.2 :μM. The signal was mediated by the B2-receptor subtype as confirmed using the specific antagonist Hoe 140. Both the onset and the intensity of the calcium signals were concentration-dependent. The rise of nuclear calcium level was independent of extracellular calcium and suppressed by thapsigargin which is known to deplete inositol 1,4,5-trisphosphate-sensitive calcium stores. Bradykinin-induced calcium increase desensitizes rapidly. This desensitization was shown not to involve activation of protein kinase C. © 1995 Wiley-Liss, Inc. |
