Evidence for in vitro expression of B1 receptor in the mouse trachea and urinary bladder

1 Motor responses to des-Arg(9)-bradykinin and bradykinin were studied in the isolated mouse trachea (precontracted with carbachol, 10 mu M) and the urinary bladder df either Swiss, C57B1/6J or bradykinin B-2 receptor knockout (Bk2r(-/-)) mice after 1-6 h in vitro. The expression of mRNA for the mouse B-1 receptor in tracheal and urinary bladder tissues was also studied by using Northern blot analysis. 2 In isolated tracheae, des-Arg(9)-bradykinin produced a relaxant response that increased over time: no response was observed after 1 h of incubation, whereas after 6 h the maximum response (1 mu M) was 68-84% of the relaxation produced by isoproterenol (1 mu M) in the three mouse strains. The relaxant response to bradykinin (1 mu M) observed at 1 h (38-51% of isoproterenol) was increased (62-65% of isoproterenol) after 6 h in Swiss and C57B1/6J mice, but was absent in Bk2r(-/-) mice. In the presence of cycloheximide, des-Arg(9)-bradykinin did not cause any response at 6 h. 3 Similar findings were obtained in the urinary bladder: at 1 h des-Arg(9)-bradykinin (1 mu M) did not cause any motor effect, whereas at 6 h it caused a contraction that was 28-59% of that produced by carbachol (1 mu M) in the three mouse strains. Cycloheximide blocked the response to des-Arg(9)-bradykinin. Bradykinin (1 mu M) contracted urinary bladders at 1 h (34-35% of carbachol), as well as at 6 h (66-77% of carbachol) in Swiss and C57B1/6J strains, but was without effect in Bk2r(-/-) mice. 4 Northern blot hybridization with a specific cDNA probe against mouse B-1 receptor mRNA using total RNA extracted from tracheae and urinary bladders freshly removed from Swiss and Bk2r(-/-) mice revealed minimal expression. However, marked hybridization was detected 150 min after in vitro exposure in both tissues. 5 Evidence is provided that in vitro exposure of mouse trachea and urinary bladder causes a time-dependent induction of B-1 receptors that cause relaxation and contraction, respectively.