Characteristics of the bradykinin-induced changes in intracellular calcium ion concentration of single bovine tracheal smooth muscle cells.
1. Single bovine tracheal smooth muscle (BTSM) cells were cultured and used to measure bradykinin-induced changes in [Ca2+]i by dynamic video imaging. 2. Bradykinin (10 pM-10 microM)-induced an increase in [Ca2+]i over basal levels (69 +/- 2 nM; n = 353) which was concentration-dependent (log EC50 = -8.7 M) in the presence of extracellular calcium ions (2 mM). The bradykinin B2 receptor antagonist, D-Arg[Hyp3,Thi5,8,D-Phe7]- bradykinin, produced a parallel shift to the right of the bradykinin concentration-response curve (log EC50 = -7.1 M and -5.8 M in the presence of 1 microM and 10 microM antagonist respectively) yielding an apparent KD of 26 nM. 3. In the absence of extracellular calcium ions (with 0.1 mM EGTA), bradykinin (10 pM-10 microM) produced a uniform increase in [Ca2+]i from a basal level of 33 +/- 2 nM (n = 140) to approximately 180 nM in BTSM cells indicating an 'all-or-nothing' release of intracellular calcium ions. In the presence of 10 microM D-Arg[Hyp3,Thi5,8,D-Phe7]-bradykinin no responses could be induced by bradykinin at concentrations below 100 nM. However, at 100 nM and 1 microM bradykinin there was no change in the uniform increase in [Ca2+]i in these cells previously observed. 4. In both the absence or presence of D-Arg[Hyp3,Thi5,8,D-Phe7]-bradykinin, there was a concentration-dependent increase in the percentage of cells responding to bradykinin (frequency) under calcium-rich or calcium-free conditions. Individual cells also demonstrated a difference in the sensitivity to any particular concentration of bradykinin. 5. A latency in the response of cells to bradykinin was observed both in calcium-containing and calcium-free conditions.6. We conclude that bradykinin B2 receptors are expressed by BTSM cells and are involved in the bradykinin-induced increase in [Ca2+]i. It appears that the increase in [Ca2+], can be mediated via a graded influx of calcium ions from the extracellular space or an 'all-or-nothing' release from intracellular stores.
Marsh
K A
KA
Department of Physiology & Pharmacology, University of Nottingham Medical School, Queen's Medical Centre.
Hill
S J
SJ
D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology*; D065168:Bradykinin Receptor Antagonists; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D007091:Image Processing, Computer-Assisted; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D018002:Receptors, Bradykinin / Q000187:drug effects; D014132:Trachea / Q000187:drug effects
D065168:Bradykinin Receptor Antagonists; D018002:Receptors, Bradykinin; C074544:bradykinin, 1-adamantanecarboxylic acid-Arg(0)-Hyp(3)-Thi(5,8)-Phe(7)-; D000218:Adamantane; D001920:Bradykinin; D002118:Calcium