Effects of dexamethasone, and protein kinase C inhibitors on the induction of bradykinin B1 mRNA and the bradykinin B1 receptor-mediated contractile response in isolated rat ileum

We detected the expression of inducible bradykinin (BK) B-1 receptor mRNA in the rat ileum by the reverse transcriptase-polymerase chain reaction (RT-PCR) method, when the isolated ileum was suspended for at least 1 hr in an aerated Tyrode's solution at 37degrees. The induction of this mRNA was both time- and temperature-dependent, and was followed by a contractile response to des-Arg(9)-BK at around 3 hr of incubation; this response increased in magnitude with time and was maximal at 6 hr. In contrast, the contraction in response to BK and the expression of B-2 receptor mRNA were constant throughout this 6-hr incubation period. The contraction due to des-Arg(9)-BK was selectively suppressed by B-1 receptor antagonists, i.e. des-Arg(9)[Leu(8)]-BK and des-Arg(10)-HOE140, but not by the B-2 antagonists D-Arg[Hyp(3),Thi(5,8) D-Phe(7)]-BK and HOE 140. The inducible des-Arg(9)-BK contractile response was suppressed by continuous in vitro exposure of the ileum to cycloheximide or actinomycin D, but neither inhibitor affected the contraction induced by BK, suggesting that the B-1 receptor could be induced de novo. In vitro and ex vivo treatment of the ileum with dexamethasone suppressed the induction of the contractile response to des-Arg(9)-BK, but had no significant effect on the expression of B-1 receptor mRNA. Some protein kinase C inhibitors, i.e. H7 and calphostin C, suppressed the expression of B-1 receptor mRNA and diminished the contractile response to des-Arg(9)-BK. These results suggest that the de novo synthesis of the B-1 receptor in the ileum preparation can be up-regulated at the transcriptional level (a process in which a specific isoform of protein kinase C may be involved). Additionally, these data suggest that the contractile response to des-Arg(9)-BK involves a process sensitive to some post-transcriptional action of dexamethasone. (C) 2002 Elsevier Science Inc. All rights reserved.