Pharmacological characterization of bradykinin B-1 and B-2 receptors in IMR-90 and INT-407 human cell lines using a microphysiometer

1. In the present study, we used a microphysiometer to measure bradykinin-i nduced acidification responses in IMR-90, a human lung fibroblast cell line , and INT-407, a human colonic epithelial cell line. Furthermore, we invest igated the effect of 24 h exposure of transforming growth factor (TGF)-alph a on the bradykinin response in INT-407 cells. 2. Bradykinin (0.1-100 nmol/L) was potent in producing acidification respon ses in IMR-90 cells (pEC(50) 8.79 +/-0.13; Hill slope 0.96 +/-0.04) and INT -407 cells (pEC(50) 8.90 +/-0.04; Hill slope 1.00 +/-0.07). These responses were competitively antagonized by the bradykinin B-2 receptor antagonist i catibant in both IMR-90 cells (apparent pK(B) = 8.54 +/-0.15; Hill slope = 1.09 +/-0.13 and 1.66 +/-0.26 in the absence and presence of 10 nmol/L icat ibant, respectively) and INT-407 cells (pK(B) = 8.12 +/-0.07 (3, 10 and 30 nmol/L icatibant); Hill slope = 1.06 +/-0.04). However, the bradykinin B-1 receptor antagonist des-Arg(9)Leu(8)-bradykinin (3 mu mol/L) had no effect on the bradykinin responses. 3. The non-peptide bradykinin B-2 receptor antagonist FR173657 selectively antagonized bradykinin-induced acidification responses in INT-407 cells in a competitive manner (pK(B) = 8.76 +/-0.10; Hill slope = 0.92 +/-0.05) at l ower concentrations (1 and 3 nmol/L) but in an insurmountable manner at hig her concentrations (10 nmol/L; Hill slope = 1.04 +/-0.09). This compound, a t concentrations of 10 and 100 nmol/L (Hill slope = 1.38 +/-0.15), also pro ved to be an insurmountable antagonist in IMR-90 cells. 4. The bradykinin B-1 receptor selective agonist Lys(0)des-Arg(10)-bradykin in (0.1 nmol/L to 0.1 mu mol/L) failed to produce acidification responses i n IMR-90 cells, even after 24 h pre-incubation with bacterial lipopolysacch aride (0.1 mug/mL). 5. A 24 h pre-incubation of INT-407 cells with TGF-alpha (1, 10 and 100 ng/ mL) caused a significant concentration-dependent decrease in maximal bradyk inin response without affecting the pEC(50). 6. In addition to this study being the first to use a microphysiometer to c haracterize bradykinin B-2 receptors in cultured IMR-90 human lung fibrobla st cells and INT-407 human colonic epithelial cells, we also showed that pr e-incubation of INT-407 cells with TGF-alpha caused a significant decrease in maximal acidification response mediated by bradykinin B-2 receptors.