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

Abstract

• 1. 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).

• 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.

• 3. The cells desensitize upon repeated addition of bradykinin.

• 4. 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⁺.

• 5. 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.

• 6. 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.