Pharmacological and molecular evidence for kinin B1 receptor expression in urinary bladder of cyclophosphamide-treated rats

Abstract

1 In the present study, we developed an experimental model of cystitis induced by cyclophosphamide (CYP). In order to characterize des-Arg9-BK-induced contraction on the urinary bladder (UB) during the development of inflammation and to quantify kinin B1 receptor gene expression using a quantitative RT-PCR technique. 2 In the presence of peptidase inhibitors captopril (10 μM), DL-thiorphan (1 μM) and DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid (MERGEPTA 5 μM), bradykinin (BK) (0.3-3000 nM) evoked a concentration-dependent contraction of rat UB which was not different between the CYP- and vehicle-treated groups. Unlike BK, des-Arg9-BK (0.3-100,000 nM) did not contract UB from vehicle-treated rats but contracted vigorously bladder strips from CYP-treated rats 14, 24 and 168 h after treatment. In UB of 24 h treated rat, the pD2 value of des-Arg9-BK was 7.3 ± 0.1. 3 The cyclo-oxygenase inhibitor indomethacin (3 μM) reduced by 30% the maximal response of des-Arg9-BK. Both the kinin B1 receptor antagonists des-Arg9-[Leu8]BK (10 μM) and des-Arg10-Hoe 140 (10 μM) produced a rightward shift of the concentration-response curve to des-Arg9-BK yielding pK(B) values of 6.8 ± 0.2 and 7.2 ± 0.1, respectively, whilst the kinin B2 receptor antagonist Hoe 140 (1 μM) had no effect. 4 After CYP treatment, mRNA coding for the kinin B1 receptor appeared predominantly in UB. In this organ, the induction was progressive, reaching a maximum 48 h after CYP treatment. 5 In conclusion, the present study provides strong evidence for an induction of kinin B, receptors in UB of CYP-treated rats. This was associated at a molecular level with an increase in mRNA expression of the gene coding for the kinin B1 receptor. This kinin receptor displayed the whole features of a classical rat kinin B1 receptor.