BRADYKININ-EVOKED RELEASE OF [H-3] NORADRENALINE FROM THE HUMAN NEUROBLASTOMA SH-SY5Y

Bradykinin (BK) evoked [H-3]noradrenaline ([H-3]NA) release from the h uman neuroblastoma SH-SY5Y and this was enhanced by pre-treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) for 8 min. This effect of BK was inhibited by 500 mu M [D-Phe(7)]BK and 100 mu M [Thi(5,8),D-Phe (7)]BK but not by 500 mu M [Des-Arg(9),Leu(8)]BK. The BK (B-1)-agonist [Des-Arg(9)]BK did not evoke [H-3]NA release. This suggested that SH- SY5Y expressed BK (B-2)-receptors coupled to the release of [H-3]NA. B K acting at B-2-receptors, also elevated intracellular calcium and dep olarized SH-SY5Y cells. Although pre-treatment of SH-SY5Y cells with T PA enhanced BK-evoked [H-3]NA release, the elevation of intracellular calcium [Ca2+]; was decreased by about 50%. BK-evoked release of [H-3] NA in cells not pre-treated with phorbol ester was only 23% dependent on extracellular calcium. In comparison, following phorbol ester treat ment approximately 40% of [H-3]NA release was dependent on extracellul ar calcium. Nifedipine (5 mu M), CoCl2 (1 mM) and NiCl2, (1 mM) inhibi ted NA release in SH-SY5Y cells pre-treated with TPA by 16.0, 47 and 4 4%, respectively. The results of this study showed that BK, acting at B-2-receptors, activated [H-3]NA release in SH-SY5Y. Part of this effe ct appeared to be due to activation of L-type calcium channels but the majority of BK-evoked [H-3]NA release in SH-SY5Y cells appeared to de pend on [Ca2+](i).