Contribution of prostaglandin E2 to bradykinin-induced contraction in rabbit urinary detrusor.
-
- NAKAHATA Norimichi
- Department of Pharmacology, Fukushima Medical College
-
- ONO Tomoyuki
- Department of Pharmacology, Fukushima Medical College
-
- NAKANISHI Hironori
- Department of Pharmacology, Fukushima Medical College
抄録
Bradykinin (100 pM to 1 μM) contracted the rabbit urinary detrusor in vitro. The sensitivity to bradykinin was about 1000 times higher than that to acetylcholine (ACh) on a molar basis. The contractile response to bradykinin was unaffected by atropine, diphenhydramine, FPL-55712, methysergide, prazosin or tetrodotoxin, indicating that the contraction was not mediated via the release of ACh, histamine, peptide leukotrienes, serotonin or catecholamine. The bradykinininduced contraction was, however, inhibited by indomethacin (5 μM), a cyclooxygenase inhibitor. Caffeic acid (10 μM), a lipoxygenase inhibitor, did not affect the contraction. Bradykinin (1 nM to 100 nM) stimulated the release of prostaglandin E2 from the detrusor in a concentration-dependent manner, and the release was abolished by treatment with indomethacin (5 μM). Prostaglandin (PG) E2 contracted the urinary detrusor with an EC50 of about 0.1 μM. Adenosine 5'-triphosphate (ATP), a stimulator of PG synthesis, also contracted the muscle with an EC50 of about 100 μM. [14C]Arachidonic acid was converted to PGE2 and F2α when it was incubated with the 700×g supernatant of the muscle homogenate. However, neither bradykinin nor ATP stimulated the PG synthesis in the supernatant. These results showed that bradykinin and ATP did not affect the cyclooxygenase and/or PG degradation system. On the other hand, when the intact detrusor muscle was incubated with [14C]arachidonic acid, bradykinin and ATP stimulated the PG synthesis, and the stimulated synthesis was inhibited by indomethacin. Mepacrine, a phospholipase A2 inhibitor, more potently inhibited the bradykinin and ATP-induced contractions than the ACh-induced one. Therefore, bradykinin as well as ATP would stimulate phospholipase, probably the A2-type, after binding of its receptor, and contract rabbit urinary detrusor mediated via PGE2 converted from arachidonic acid.
収録刊行物
-
- Jpn.J.Pharmacol.
-
Jpn.J.Pharmacol. 43 (4), 351-359, 1987
公益社団法人 日本薬理学会