Bradykinin causes a transient rise of intracellular Ca2+-activity in cultured neural cells

The concentration of intracellular free calcium ions was measured by spectrofluorometry in suspensions of quin2 loaded neural cell lines: neuroblastoma X glioma hybrid cells (clones 108CC15 and 108CC25) and polyploid rat glioma cells (clone C6-4-2). In these cells, bradykinin elicits a transient increase of the cytosolic Ca2+-activity in a dose-dependent manner (half-maximal effect at about 10 nM). The effect requires the presence of extracellular Ca2+. The time to peak is at most 10 s, the decay to the original level lasts 1 min and is followed by a period of 1-4 min during which Ca2+ activity is slightly below control value. Lys-bradykinin and Met-Lys-bradykinin evoke similar effects as bradykinin, but at concentrations 10 times lower. The cells desensitize upon repeated addition of bradykinin. Under the same conditions des-Arg1-bradykinin, des-Arg9-bradykinin, angiotensin II, substance P, apamin and histamine exerted no influence on the concentrations of free Ca2+. Similar to their effect in neural cell lines, bradykinin and Lys-bradykinin induce in primary astroglia-rich cultures from rat brain an increase in the concentration of cytosolic Ca2+ with the peak reached within 30 s and the decay to the original level lasting approximately 4 min. The significance of this effect of bradykinin on the cytosolic Ca2+-activity is discussed in relation to previous findings that bradykinin in the same cell lines induces a hyperpolarization, a rise of the cyclic GMP level and a breakdown of phosphoinositides.