Des‐Arg9‐bradykinin‐induced increases in intracellular calcium ion concentration in single bovine tracheal smooth muscle cells

Abstract

1. Dynamic video imaging was used to measure the des-Arg9-bradykinin-induced changes in the intracellular free calcium ion concentration ([Ca2+]i) of single bovine tracheal smooth muscle (BTSM) cells. 2. In the presence of extracellular calcium ions, des-Arg9-bradykinin (1 nM-10 microM) produced a concentration-dependent increase in the [Ca2+]i over basal levels yielding an EC50 value of 316 nM. The percentage of cells responding to each concentration of des-Arg9-bradykinin also increased in a concentration-dependent manner (from 9% to 100%). 3. The bradykinin B2 receptor antagonist, D-Arg[Hyp3,Thi5,8,D-Phe7]-bradykinin (10 microM), was without effect on the calcium response of the cells when added 2 min prior to des-Arg9-bradykinin (100 nM). However, the B1 receptor antagonist, des-Arg9Leu8-bradykinin (10 microM), completely abolished the des-Arg9-bradykinin-induced response. 4. Under calcium-free conditions, des-Arg9-bradykinin induced an increase in [Ca2+]i at concentrations of 1 microM and 10 microM. The response to 10 microM des-Arg9-bradykinin was reduced by preincubation of either D-Arg[Hyp3, Thi5,8,D-Phe7]-bradykinin (10 microM) or des-Arg9Leu8-bradykinin (10 microM). 5. We conclude that bradykinin B1 receptors are expressed by cultured BTSM cells and mediate the des-Arg9-bradykinin-induced influx of calcium ions at low agonist concentrations (< 1 microM). At higher concentrations, des-Arg9-bradykinin (1 microM and 10 microM) can stimulate both B1 and B2 receptors to effect intracellular calcium release under calcium-free conditions.