Abstract

We have assessed the effect of bradykinin and histamine on the cytosolic free calcium concentration ([Ca2+](i)) of bovine adrenal medulla capillary endothelial cells (BAMCECs). To measure [Ca2+](i) changes in BAMCECs the intracellular fluorescent probe, fluo-3 AM, was used. Bradykinin (3 mu M) produced a transient monophasic increase in [Ca2+](i), which was depressed by B1650 (0.1 mu M), a B2-bradykinin receptor antagonist (D-Arg-[Hyp(3), Thi(5,8), D-Phe(7)]-Bradykinin). Similarly, increase in [Ca2+](i) induced by histamine was also depressed by tripolidine (0.1 mu M), an H1-histamine receptor antagonist. [Ca2+](i) increase induced by both agonists was unaffected in the absence of extracellular Ca2+ or presence of antagonists of voltage operated Ca2+ channels (VOCCs). Thapsigargin (1 mu M) did not abolish the increase of [Ca2+](i) produced by bradykinin, but abolished that of histamine. In contrast, caffeine (100 mu M), abolished the [Ca2+](i) response induced by bradykinin (3 mu M), but did not affect the [Ca2+](i) increase induced by histamine (100 mu M). The results indicate the presence of B2 bradykinin-and H1 histamine-receptors in BAMCECs. Liberation of Ca2+ induced by both agonists occurs through 2 different intracellular mechanisms. While bradykinin activates a sarco(endo) plasmic reticulum (SER) containing a SER Ca2+-ATPase (SERCA) thapsigargin-insensitive, histamine activates a SER containing a SERCA thapsigargin-sensitive. We suggest that the increase in [Ca2+](i) induced by bradykinin and histamine could be of physiological relevance, modulating adrenal gland microcirculation.