Contribution of nitric oxide, prostanoids and Ca(2+)-activated K+ channels to the relaxant response of bradykinin in the guinea pig bronchus in vitro.
In the guinea pig bronchus with epithelium, pre-contracted with histamine, bradykinin (BK), lysyl-BK, prostaglandin E2 (PGE2), cromakalim and S-nitroso-N-acetylpenicillamine each caused graded relaxation with mean EC50s of 34 nM, 11 nM, 0.1 nM, 0.3 microM and 3.4 microM, respectively. The addition of NO synthase inhibitors N(W)-nitro-L-arginine (L-NOARG), N(G)-monomethyl-L-arginine or 7-nitroindazole reduced BK-induced relaxation by 41+/-6%, 59+/-4% and 51+/-2%, respectively. The inhibition of BK response caused by L-NOARG was completely reversed by L-, but not by D-arginine. Methylene blue and 6-(phenylamino)-5,8-quinolinedione (LY 83583) inhibited the BK response by 88+/-5% and 64+/-4%, while 1H-[1,2,4]oxadiazolo[4,3-a]quinolaxin- -one (ODQ) had no effect. However, ODQ almost abolished SNAP-induced relaxation. Indomethacin and the cyclo-oxygenase 2 (COX-2) inhibitor 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanon e (DFU) caused graded inhibtion of BK responses with mean IC50s of 60 nM and 0.6 nM, respectively. Addition of tetraethylammonium (TEA), charybdotoxin (ChTx), or iberotoxin (IbTx) inhibited BK-induced relaxation by 76+/-4%, 30+/-4% and 99+/-1%, respectively, but the relaxations of PGE2 and cromakalim were unaffected. In contrast, 4-aminopyridine, apamin or glibenclamide did not affect BK-induced relaxation. These results indicate that BK-induced epithelium-dependent relaxation in the guinea pig bronchus is partially mediated by release of NO or by NO-related substances, involving an activation of both cyclo-oxygenase 1 (COX-1) and COX-2 enzymes, through a cyclic guanosine monophosphate (cGMP)-independent mechanism. Furthermore, BK-induced relaxation involves an activation of high-conductance Ca(2+)-activated K+ channels highly sensitive to IbTx, and to a lesser extent to ChTx and TEA.
Mazzuco
T L
TL
Department of Pharmacology, Centre of Biological Sciences, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
André
E
E
Calixto
J B
JB
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology / Q000502:physiology*; D001980:Bronchi / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005260:Female; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D015221:Potassium Channels / Q000502:physiology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000502:physiology*
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D015221:Potassium Channels; D011453:Prostaglandins; D016718:Arachidonic Acid; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D001920:Bradykinin; D002118:Calcium