M. Trevisani et al., Evidence for in vitro expression of B-1 receptor in the mouse trachea and urinary bladder, BR J PHARM, 126(6), 1999, pp. 1293-1300
1 Motor responses to des-Arg(9)-bradykinin and bradykinin were studied in t
he isolated mouse trachea (precontracted with carbachol, 10 mu M) and the u
rinary bladder df either Swiss, C57B1/6J or bradykinin B-2 receptor knockou
t (Bk2r(-/-)) mice after 1-6 h in vitro. The expression of mRNA for the mou
se 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 relaxati
on produced by isoproterenol (1 mu M) in the three mouse strains. The relax
ant response to bradykinin (1 mu M) observed at 1 h (38-51% of isoprotereno
l) 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, d
es-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 cause
d a contraction that was 28-59% of that produced by carbachol (1 mu M) in t
he three mouse strains. Cycloheximide blocked the response to des-Arg(9)-br
adykinin. 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 relax
ation and contraction, respectively.