Bradykinin-stimulated calcium mobilization in cultured canine tracheal smooth muscle cells.
Bradykinin (BDK)-induced increases in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) using a fluorescent Ca2+ indicator, Fura-2. BDK and kallidin caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner, with half-maximal stimulation (log EC50) obtained at -8.10 M and -8.04 M, respectively. The BDK-induced rise in [Ca2+]i was not affected by the BDK B1 receptor antagonist, des-Arg9[Leu8]-BDK (10 microM). However, the BDK B2 receptor antagonists des-Arg[Hyp3, Thi5,8, D-Phe7]-BDK and Hoe 140 had high affinity in antagonizing BDK with pKB values of 7.5 +/- 0.3 and 8.7 +/- 0.3, respectively. The sustained phase of the rise in [Ca2+]i was dependent on the presence of external Ca2+, as evidenced by a decline to the resting level on addition of EGTA. In the absence of external Ca2+, only an initial transient peak was seen which then declined to the resting level; a sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of BDK. Ca2+ influx was required for the changes in [Ca2+]i, since Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to BDK. In conclusion, these findings indicate that the initial increase in [Ca2+]i stimulated by BDK acting on BDK B2 receptors is due to the release of Ca2+ from internal stores, followed by the influx of external Ca2+ into the cells. The influx of extracellular Ca2+ partially involves a diltiazem- and verapamil-sensitive Ca2+ channel.
Yang
C M
CM
Department of Pharmacology, Chang Gung Medical College, Tao-Yuan, Taiwan, Republic of China.
Hsia
H C
HC
Hsieh
J T
JT
Ong
R
R
Luo
S F
SF
D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D016257:Fura-2; D007609:Kallidin / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D014132:Trachea / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
C058532:HOE k86-4321; D007609:Kallidin; D004533:Egtazic Acid; C051090:bradykinin, Leu(8)-des-Arg(9)-; C065679:icatibant; D002217:Carbachol; D014700:Verapamil; D004110:Diltiazem; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2