Selectivity of bradykinin analogues for receptors mediating contraction and relaxation of the rat duodenum.
1. Bradykinin produces a biphasic response in the rat duodenum that consists of a relaxation (pD2 = 8.44) followed by a contraction (pD2 = 6.91). 2. The B1 agonist des-Arg9-bradykinin produced a contraction (pD2 = 7.16) but no relaxation. Des-Arg9-[Leu8]-bradykinin, which is a B1 antagonist in other systems produced contraction (pD2 = 7.65) in the rat duodenum. 3. Four bradykinin analogues that are preferential B2 agonists in other tissues had a biphasic effect with pD2 values in the range 7.22-8.68 for relaxation and 6.26-6.91 for contraction. 4. [Thi5,8,D-Phe7]-bradykinin, which is a B2 antagonist in most other systems produced relaxation in the rat duodenum, with a pD2 of 7.49. 5. It is concluded that the contractile component of the response to bradykinin in rat duodenum may be mediated by a subtype of the B1 receptor and the relaxant component by a receptor of the B2 subtype.
Paiva
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Department of Biophysics, Escola Paulista de Medicina, Sao Paulo, Brazil.
Paiva
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TB
Pereira
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CC
Shimuta
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SI
D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D004386:Duodenum / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; D001920:Bradykinin