Bradykinin B2- and 5-hydroxytryptamine (5-HT2)-receptor stimulated increases in intracellular calcium in cultured guinea-pig aortic smooth muscle cells.
The effect of 5-hydroxytryptamine (5-HT) and bradykinin on intracellular free calcium concentration ([Ca2+]i) has been studied in cultured guinea-pig aortic smooth muscle cells loaded with the Ca(2+)-sensitive fluorescent dye fura-2. Bradykinin and 5-HT elicited rapid increases in [Ca2+]i with log EC50 values of -7.9 +/- 0.05 M (N = 3) and -6.1 +/- 0.1 M (N = 4), respectively. Both agonists stimulated the release of intracellular calcium (Ca2+ responses still present in the absence of extracellular calcium) and to a lesser extent Ca2+ influx (observed when extracellular calcium was re-applied to cells initially stimulated in nominally Ca(2+)-free buffer containing 0.1 mM EGTA). The B1-receptor antagonist des-Arg9,[Leu8]-bradykinin had no effect on calcium responses elicited 100 nM bradykinin, whereas the B2-receptor antagonist D-Arg[Hyp3,Thi5.8,D-Phe7]-bradykinin (10 microM) inhibited the response to 100 nM bradykinin by 43%. The bradykinin B2-receptor antagonist D-Arg[Hyp3,Thi5.8,D-Phe7]-bradykinin virtually abolished the response to 10 nM bradykinin (IC50 4 microM). No increase in [Ca2+]i was observed with the B1-receptor agonist des-Arg9-bradykinin (300 nM). The response to 5-HT (100 microM) was abolished by the 5-HT2 receptor antagonist ketanserin (IC50 = 2 +/- 0.4 nM; N = 3). These data suggest that in cultured guinea-pig aortic smooth muscle cells bradykinin B2- and 5-HT2-receptor activation stimulates the release of Ca2+ from intracellular stores and Ca2+ influx through Ca2+ entry pathways in the plasma membrane.
Dickenson
J M
JM
Department of Medicine, Medical School, Queen's Medical Centre, Nottingham, U.K.
Bulmer
S
S
Whittaker
A
A
Salwey
M
M
Hawley
J
J
Hill
S J
SJ
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006168:Guinea Pigs; D007150:Immunohistochemistry; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D018002:Receptors, Bradykinin / Q000187:drug effects*; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology
D018002:Receptors, Bradykinin; D011985:Receptors, Serotonin; D012701:Serotonin; D001920:Bradykinin; D002118:Calcium