Bradykinin and histamine‐induced cytosolic calcium increase in capillary endothelial cells of bovine adrenal medulla

We have assessed the effect of bradykinin and histamine on the cytosolic free calcium concentration ([Ca 2a ]i) of bovine adrenal medulla capillary endothelial cells (BAMCECs). To measure [Ca 2a ]i changes in BAMCECs the intracellular fluorescent probe, fluo-3 AM, was used. Bradykinin (3 mM) produced a transient monophasic increase in [Ca 2a ]i, which was depressed by B1650 (0.1 mM), a B2-bradykinin receptor antagonist (D-Arg-[Hyp 3 , Thi 5,8 , D-Phe 7 ]-Bradykinin). Similarly, increase in [Ca 2a ]i induced by histamine was also depressed by tripolidine (0.1 mM), an H1-histamine receptor antagonist. [Ca 2a ]i increase induced by both agonists was unaffected in the absence of extracellular Ca 2a or presence of antagonists of voltage operated Ca 2a channels (VOCCs). Thapsigargin (1 mM) did not abolish the increase of [Ca 2a ]i produced by bradykinin, but abolished that of histamine. In contrast, caffeine (100 mM), abolished the [Ca 2a ]i response induced by bradykinin(3 mM),butdidnotaffectthe[Ca 2a ]iincreaseinducedbyhistamine(100 mM).Theresultsindicatethepresenceof B2 bradykinin- and H1 histamine-receptors in BAMCECs. Liberation of Ca 2a induced by both agonists occurs through 2 differentintracellularmechanisms.Whilebradykininactivatesasarco(endo)plasmicreticulum(SER)containingaSERCa 2a ATPase (SERCA) thapsigargin-insensitive, histamine activates a SER containing a SERCA thapsigargin-sensitive. We suggest that the increase in [Ca 2a ]i induced by bradykinin and histamine could be of physiological relevance, modulating adrenal