Mechanisms for activation and subsequent removal of cytosolic Ca 2+ in bradykinin-stimulated neuronal and glial cell lines

• Published in: Experimental cell research Vol. 186; no. 1; pp. 47 - 53
• Main Authors: Reiser, Georg, Binmöller, Franz-Josef, Donié, Frédéric
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1990
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/0014-4827(90)90208-R

Mechanisms for activation and for removal of cytosolic Ca 2+ after stimulation with bradykinin were investigated in two neural cell lines by measuring cytosolic Ca 2+ activity and 45Ca 2+ fluxes. In the neuronal (neuroblastoma X glioma hybrid) and in the glial (rat glioma) cell lines, the transient, bradykinin-induced rise in cytosolic Ca 2+ activity (determined by fura-2 or indo-1 fluorescence) was blocked by a bradykinin B 2 receptor antagonist. Ca 2+ ionophores (ionomycin and 4-Br-A23187) caused a comparable transient rise in cytosolic Ca 2+ activity. After addition of ionophores, the Ca 2+ response to bradykinin was reduced or completely blocked in both cell lines. At the concentrations used, the ionophores primarily depleted intracellular Ca 2+ stores and prevented refilling of the stores. Thus, the bradykinin-induced rise of cytosolic Ca 2+ activity seems to be mostly due to Ca 2+ release from internal stores. In the neuronal but not in the glial cell line, a brief stimulation by bradykinin of 45Ca 2+ uptake was followed by a long-lasting inhibition below control values. Thus, in the neuronal cells bradykinin presumably blocks Ca 2+ channels by a readily reversible, pertussis toxin-insensitive mechanism. Excess cytosolic Ca 2+ of the bradykinin-stimulated cells is mostly not resequestered into the internal Ca 2+ pool accessible to bradykinin, but is mainly extruded through the plasma membrane, as indicated by (i) stimulation of 45Ca 2+ release by bradykinin, (ii) quick reduction by bradykinin of cellular 45Ca 2+ content of cells preequilibrated with 45Ca 2+, and (iii) diminution of the ionophore-inducible Ca 2+ response after the addition of bradykinin.