bradykinin--met-lys- and icatibant

This study was designed to investigate the mechanisms by which bradykinin induces contraction of the pig iris sphincter muscle in vitro. Addition of bradykinin, Lys-bradykinin and Met-Lys-bradykinin to the pig iris sphincter resulted in a graded contraction with a mean EC(50s) of 21, 11 and 5 nM, respectively. The bradykinin B(1) receptor agonist des-Arg(9)-bradykinin only caused a slight contraction, measured 6 h after the tissue was set up. The B(2) receptor antagonists FR 173657 ((E)-3-(6-acetamido-3-pyridyl)-N [N-2-4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylamino-carbonyl-ethyl] acrylamide) and Hoe 140 (D-Arg(0)-[Hyp(3), Thi(5), D-Tic(7), Oic(8)]-bradykinin produced a graded shift to the right associated with marked inhibition of the bradykinin-induced contraction. Atropine, guanethidine or tetrodotoxin significantly reduced the bradykinin-induced contraction. Dazoxiben, an inhibitor of thromboxane A(2), and MK-571 (3-(3-(2-(7-chloro-2-quinolinyl) ethenyl) phenyl ((3-dimethyl amino-3oxo-propyl) thio) methyl) propanoic acid, a leukotriene D(4) receptor-selective antagonist, also caused inhibition of the bradykinin-mediated contraction. Cyclooxygenase-1 and -2 inhibitors, indomethacin, ibuprofen, valeryl salicylate and NS 398 (N-[2-(cyclohexyloxy)-4-nitrophenyl]methanosulfonamide) all significantly inhibited the bradykinin-mediated contraction without affecting the carbachol-induced contraction of the pig iris sphincter. Taken together, these results indicate that the bradykinin-mediated contraction of the pig iris sphincter muscle seems to be mediated primarily by the activation of the B(2) receptor release of acetylcholine, noradrenaline and both cyclooxygenase-1 and -2 metabolites besides the release of leukotriene D(4) and tromboxane A(2) from the arachidonic acid pathway.

Topics: Animals; Atropine; Bradykinin; Bradykinin Receptor Antagonists; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanethidine; Ibuprofen; Imidazoles; In Vitro Techniques; Indomethacin; Iris; Kallidin; Muscle Contraction; Muscle, Smooth; Nitrobenzenes; Propionates; Quinolines; Salicylates; Sulfonamides; Swine; Tetrodotoxin; Thromboxane-A Synthase

To characterize the kinin receptor subtype involved in the relaxation of human isolated corpus cavernosum (HCC) induced by bradykinin (BK), Lys-bradykinin (Lys-BK), Met-Lys-bradykinin (Met-Lys-BK) and des-Arg9-bradykinin, and to investigate whether the kinin-induced relaxation of HCC results from the stimulation of nonadrenergic, noncholinergic (NANC) neurons supplying the cavernosal tissue.. Excised HCC tissues were immediately placed in Krebs solution and kept at 4 degrees C until use (never > 24 h after removal). HCC was cut in strips of approximately 2 cm, suspended in a cascade system and superfused with oxygenated and warmed Krebs solution at 5 mL/min. After equilibration for approximately 90 min, noradrenaline (3 micromol/L) was infused to induce a submaximal contraction of the HCC strips. The release of cyclo-oxygenase products was prevented by infusing indomethacin (6 micromol/L). HCC strips were calibrated by injecting a single bolus of the nitrovasodilator glyceryl trinitrate (GTN) and the sensitivity of the tissues adjusted electronically to be similar. The agonists (kinins, histamine and acetylcholine) were injected as a single bolus (up to 100 microL) and the relaxation of HCC expressed as a percentage of the submaximal relaxation induced by GTN.. Bradykinin, Lys-BK and Met-Lys-BK significantly relaxed the HCC tissues; on a molar basis, there was no statistical difference among the degrees of relaxation induced by these peptides. The B1 kinin receptor agonist des-Arg9-bradykinin had no effect on the HCC. The infusion of the B2 kinin receptor antagonist Hoe 140 (50 nmol/L) virtually abolished the relaxation induced by BK, Lys-BK and Met-Lys-BK without affecting those induced by acetylcholine and histamine. The infusion of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester increased the tone of the HCC tissues and significantly reduced (P < 0.01) the relaxation induced by BK (74%), Lys-BK (90%), Met-Lys-BK (87%) and acetylcholine (89%) without affecting those induced by GTN. The subsequent infusion of L-arginine (300 micromol/L) partially reversed the increased tone and significantly (P < 0.01) restored the relaxation induced by BK, Lys-BK and Met-Lys-BK. The results were similar with the novel guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo[4,3,-alquinoxalin-1-one] which reduced by > 95% (P < 0.01) the relaxation induced by BK, Lys-BK, Met-Lys-BK, acetylcholine and GTN. The infusion of the sodium-channel blocker tetrodotoxin had no significant effect on the BK-, GTN- and acetylcholine-induced relaxation of HCC.. This study clearly showed the existence of functional B2 kinin receptors in human erectile tissues that when activated lead to the release of NO and hence relaxation of the HCC tissues. As tetrodotoxin failed to affect the kinin-induced relaxation of HCC strips, it is likely that these peptides release NO from the endothelium of sinusoidal capillaries rather than from neuronal sources supplying the cavernosal tissue. Although tissue kallikreins and their components have been found in the male reproductive system, the physiopathological importance of these findings has yet to be elucidated.

Topics: Adolescent; Adrenergic beta-Antagonists; Adult; Bradykinin; Bradykinin Receptor Antagonists; Enzyme Inhibitors; Humans; Kallidin; Male; Middle Aged; NG-Nitroarginine Methyl Ester; Nitric Oxide; Penile Erection; Penis; Receptors, Bradykinin