DES-ARG(9)-BRADYKININ-INDUCED INCREASES IN INTRACELLULAR CALCIUM-ION CONCENTRATION IN SINGLE BOVINE TRACHEAL SMOOTH-MUSCLE CELLS

1 Dynamic video imaging was used to measure the des-Arg(9)-bradykinin- induced changes in the intracellular free calcium ion concentration ([ Ca2+](i)) of single bovine tracheal smooth muscle (BTSM) cells. 2 In t he presence of extracellular calcium ins, des-Arg(9)-bradykinin (1 nM- 10 mu M) produced a concentration-dependent increase in the [Ca2+](i) over basal levels yielding an EC(50) value of 316 nM. The percentage o f cells responding to each concentration of des-Arg(9)-bradykinin also increased in a concentration-dependent manner (from 9% to 100%). 3 Th e bradykinin B-2 receptor antagonist, D-Arg[Hyp(3),Thi(5,8)D-Phe(7)]-b radykinin (10 mu M), was without effect on the calcium response of the cells when added 2 min prior to des-Arg(9)-bradykinin (100 nM). Howev er the B-1 receptor antagonist, des-Arg(9)leu(8)-bradykinin (10 mu M), completely abolished the des-Arg(9)-bradykinin-induced response. 4 Un der calcium-free conditions, des-Arg(9)-bradykinin induced an increase in [Ca2+](i) at concentrations of 1 mu M and 10 mu M. The response to 10 mu M des-Arg(9)-bradykinin was reduced by preincubation of either D-Arg[Hyp(3),Thi(5,8)D-Phe(7)]-bradykinin (10 mu M) or des-Arg(9)leu(8 )-bradykinin (10 mu M). 5 We conclude that bradykinin B-1 receptors ar e expressed by cultured BTSM cells and mediate the des-Arg(9)-bradykin in-induced influx of calcium ions at low agonist concentrations (<1 mu M). At higher concentrations, des-Arg(9)-bradykinin (1 mu M and 10 mu M) can stimulate both B-1 and B-2 receptors to effect intracllular ca lcium release under calcium-free conditions.