Characterization of bradykinin B2 receptors on human IMR-90 lung fibroblasts: stimulation of 45Ca2+ efflux by D-Phe substituted bradykinin analogues.
[3H]Bradykinin binds to intact human IMR-90 fetal lung fibroblasts in a time and dose-dependent manner. Binding equilibrium was attained by 120 minutes at 4 degrees C. [3H]Bradykinin binding was saturable; Scatchard analysis of saturation binding data demonstrated a single binding site having a KD = 1.8 +/- 0.2 nM and a receptor concentration of 17.4 +/- 4.0 fmol/10(5) cells. The calculated value for KD(k-1/k1) from the association (k1 = 4.71 x 10(6) mol-1 min-1) and dissociation (k-1 = 1.13 x 10(-2) min-1) rate constants was 2.4 nM. The rank order of potency observed for bradykinin peptide agonists, bradykinin > Lys-bradykinin > Met,Lys-bradykinin > Ile,Ser-bradykinin >> des-Arg9-bradykinin, is consistent with that of a bradykinin B2 receptor. Bradykinin stimulated efflux of 45Ca2+ from IMR-90 cells dose dependently with an EC50 = 331 +/- 50 pM. 45Ca2+ efflux was also demonstrated with Lys-bradykinin and Met-Lys-bradykinin but not by des-Arg10-kallidin (100 nM) or NKA (1 microM). Hoe-140 inhibited bradykinin-induced 45Ca2+ efflux (IC50 = 3 +/- 2 nM). D-Phe7-substituted bradykinin analogues stimulated 45Ca2+ efflux dose dependently and this stimulation of 45Ca2+ efflux was inhibited by Hoe-140. These results suggest that D-Phe7 substituted bradykinin analogues are agonists at the bradykinin B2 receptor in IMR-90 cells.
Sawutz
D G
DG
Department of Enzymology and Receptor Biochemistry, Sterling Winthrop Pharmaceuticals, Inc., Malvern, PA 19355.
Faunce
D M
DM
Houck
W T
WT
Haycock
D
D
D001920:Bradykinin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D002478:Cells, Cultured / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors / Q000187:drug effects*
D002132:Calcium Radioisotopes; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; C065679:icatibant; D001920:Bradykinin; D002118:Calcium