SYNERGISM IN CYTOSOLIC CA2+ MOBILIZATION BETWEEN BRADYKININ AND AGONISTS FOR PERTUSSIS TOXIN-SENSITIVE G-PROTEIN-COUPLED RECEPTORS IN NG 108-15 CELLS

Bradykinin (BK) induced a transient and pertussis toxin (PT)-insensitive increase in cytosolic Ca2+ ([Ca2+]i) in NG 108-15 neuroblastoma x glioma hybrid cells, whereas leucine-enkephalin (EK), somatostatin, norepinephrine or carbachol showed a weak but PT-sensitive action. When any one of the latter agonists was applied to the cells treated with low doses of BK, however, the level of [Ca2+]i rise caused by the agonist was remarkably increased in a PT-sensitive manner. The decreasing of extracellular Ca2+ only slightly influenced the actions of these agonists. Thus, synergism between a BK receptor and PT-sensitive G-protein-coupled receptors results in marked intracellular Ca2+ mobilization by the latter agonists.