Different Prostanoids Are Involved in Bradykinin-Induced Endothelium-Dependent and -Independent Vasoconstriction in Rat Mesenteric Resistance Arteries

J Pharmacol Sci 94, 115 – 121 (2004) Journal of Pharmacological Sciences ©2004 The Japanese Pharmacological Society Full Paper Different Prostanoids Are Involved in Bradykinin-Induced Endothelium-Dependent and -Independent Vasoconstriction in Rat Mesenteric Resistance Arteries Hideki Nawa1, Yuji Kurosaki1, and Hiromu Kawasaki1,* 1Department of Clinical Pharmaceutical Science, Graduate School of Natural Science and Technology, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan Received December 3, 2002; Accepted December 3, 2003 Abstract. Mechanisms underlying bradykinin-induced vasoconstriction were investigated in rat perfused mesenteric vascular beds with active tone. In preparations with intact endothelium, bolus injections of bradykinin (1 to 1,000 pmol) dose-dependently produced three-phase vascular effects, which consisted of a first-phase vasodilation followed by a second-phase vasoconstriction and a subsequent third-phase vasodilation; these effects were abolished by FR172357 9 8 (bradykinin B2-receptor antagonist), but not by des-Arg -[Leu ]-bradykinin (bradykinin B1-receptor antagonist). In preparations with intact endothelium, indomethacin (cyclooxygenase inhibitor), seratrodast (thromboxane A2 (TXA2)-receptor antagonist), ONO-3708 (TXA2/prostaglandin H2 (PGH2)-receptor antagonist) or ozagrel (TXA2 synthesis inhibitor) markedly inhibited the bradykinin-induced vasoconstriction. In preparations without endothelium, the bradykinin-induced vasoconstriction was abolished by indomethacin and ONO-3708, while seratrodast and ozagrel had no effect. These results suggest that the endothelium-dependent vasoconstriction of bradykinin is mainly mediated by TXA2 and that prostanoids other than TXA2, probably PGH2, in mesenteric vascular smooth muscle are responsible for bradykinin-induced endothelium-independent vasoconstriction. Keywords: bradykinin, vasoconstriction, thromboxane A2, prostaglandin H2, rat mesenteric resistance artery Introduction We previously reported that exogenous bradykinin in the rat mesenteric resistance artery induces triphasic Bradykinin is a potent endogenous vasoactive stimu- vascular responses, which consisted of an initial phase lant, mediating both vasodilation and vasoconstriction vasodilation followed by a second-phase vasoconstric- (1 – 3). Bradykinin produces vascular action via authen- tion and a third-phase gradual vasodilation (14). We also tic receptors, the B1 and B2 subtypes, in endothelial and suggested that the arachidonic acid metabolite, probably smooth muscle cells (4 – 7). The mechanisms underly- TXA2, in the mesenteric artery was responsible for the ing the vasoconstrictions depend on the tissues and the vasoconstrictor response to bradykinin (14). However, species studied (2, 8, 9). Several studies reported that the role of prostanoids in bradykinin-induced vaso- the cyclooxygenase products, prostaglandin (PG) H2 constrictor responses of the mesenteric resistance artery (PGH2), thromboxane A2 (TXA2), and PGF2, mediate remains unknown. The present study was, therefore, the contraction evoked by the peptide (10 – 12). designed to investigate precise mechanisms underlying Although the vasorelaxant effect of bradykinin is well bradykinin-induced vasoconstriction in rat mesenteric known to be endothelium- and nitric oxide (NO)-depen- resistance arteries. dent (3, 7, 13), the nature and role of its vasoconstrictor effect is unclear. Materials and Methods *Corresponding author. FAX: +81-86-251-7970 Animals E-mail: [email protected] Male Wistar rats, weighing 220 to 350 g, were used 115 116 H Nawa et al in the present study. Animals were given food and (model 975; Harvard Apparatus, Holliston, MA, USA). water ad libitum. They were housed in the Animal Injection volumes were 100 L for 12 s. Research Center of Okayama University at a controlled ambient temperature of 22 M 2LC with 50 M 10% relative Experimental protocols humidity and with a 12-h light/12-h dark cycle (lights Isolated mesenteric vascular beds were perfused with on at 8:00 a.m.). Krebs solution, and perfusion pressure was increased by perfusion with Krebs solution containing the 1-adreno- Perfusion of mesenteric vascular beds ceptor agonist methoxamine (7 M) in the presence of The animals were anesthetized with pentobarbital-Na guanethidine (5 M) that was added to exclude possible (50 mg/kg, intraperitoneally) and the mesenteric vas- involvement of vascular adrenergic nerves by blocking cular beds were isolated and prepared for perfusion as adrenergic neurotransmission. After the elevated perfu- described previously (14, 15). The superior mesenteric sion pressure stabilized, bradykinin at doses of 1, 3, 10, artery was cannulated and flushed gently with Krebs- 30, 100, 300, and 1,000 pmol were directly injected Ringer bicarbonate solution (Krebs solution) to elimi- into the perfusate using the injection pump. Injection nate blood in the vascular bed. After removal of the volumes were 100 l for 12 s. To assess the mechanisms entire intestine and associated vascular bed, the mesen- underlying the vascular effect of bradykinin, bolus injec- teric vascular bed was separated from the intestine by tions of bradykinin were performed in preparations cutting close to the intestinal wall. Only four main with intact endothelium during perfusion of the brady- 9 8 arterial branches from the superior mesenteric trunk kinin B1-receptor antagonist des-Arg -[Leu ]-bradykinin running to the terminal ileum were perfused. All other (1 M) (6); bradykinin B2-receptor antagonist branches of the superior mesenteric artery were tied FR172357 (0.1 M) (16); cyclooxygenase inhibitor off. The isolated mesenteric vascular bed was then indomethacin (0.05 and 0.5 M); TXA2-receptor antago- placed in a water-jacketed organ bath maintained at nist seratrodast (0.5 and 5 M) (Ki values 60 nM for 37LC and perfused with a modified (see below) Krebs TXA2 receptors) (17); TXA2 synthase inhibitor ozagrel solution at a constant flow rate of 5 mL/min with a (10 and 100 M) (18); and TXA2/PGH2-receptor antago- peristaltic pump (model AC-2120; ATTO Co., Tokyo). nist ONO-3708 (5 and 10 M) (Ki values 17.2 nM for Preparations were also superfused with the same solu- TXA2/PGH2 receptors) (19). tion at a rate of 0.5 mL/min to prevent drying. The To assess the influence of endothelium, the brady- Krebs solution was bubbled with a mixture of 95% O2 – kinin-induced vascular responses were examined in 5% CO2 before passage through a warming coil main- preparations with chemical removal of the endothelium tained at 37LC. Modified Krebs solution was of the by SD. After SD perfusion, the active tone of the following composition: 119.0 mM NaCl, 4.7 mM KCl, preparation was produced by perfusion with Krebs 2.4 mM CaCl2, 1.2 mM MgSO4, 25.0 mM NaHCO3, solution containing methoxamine and guanethidine 1.2 mM KH2PO4, 0.03 mM disodium EDTA, and (5 M). The concentration of methoxamine was reduced 11.1 mM dextrose (pH 7.4). Changes in the perfusion to 2 M from 7 M because the vasoconstrictor pressure were measured with a pressure transducer response was enhanced after endothelium removal. (model TP-400T; Nihon Kohden, Tokyo) and recorded After confirming successful removal of the endothelium using a pen recorder (model U-228; Nippon Denshi by the lack of a relaxant effect with 1 nmol ACh injec- Kagaku, Tokyo). tion, bradykinin injections were carried out. In preparations without endothelium, bradykinin injections were Chemical removal of vascular endothelium performed during perfusion of Krebs solution containing To remove the vascular endothelium, preparations indomethacin (0.5 M), seratrodast (5 M), ozagrel with resting tone were perfused with a 1.80 mg/mL (100 M), or ONO-3708 (10 M), and methoxamine solution of sodium deoxycholate (SD) in saline for 30 s. and guanethidine. This caused a transient increase (20 – 30 mmHg) in At the end of each experiment, preparations were perfusion pressure. Then, the preparations were rinsed perfused with 100 M papaverine to cause complete with SD-free Krebs solution for 40 min. After the relaxation. Vasodilator activity is expressed as percent- preparations were contracted by perfusion with Krebs age of the perfusion pressure at maximum relaxation solution containing methoxamine, chemical removal of induced by papaverine. Vasoconstrictor activity is ex- the endothelium was assessed by the lack of a relaxant pressed as percentage of the perfusion pressure before effect after a bolus injection of 1 nmol acetylcholine the bradykinin injection. (ACh), which was injected directly into the perfusate proximal to the arterial cannula with an injection pump Bradykinin-Induced Vasoconstriction 117 Statistical analyses Results Experimental results are presented as the means M S.E.M. Statistical analysis was evaluated by Tukey’s Vascular effect of bradykinin in rat perfused mesenteric multiple comparison test. Values of P0.05 were consid- arteries with endothelium ered to indicate statistical significance. As shown in Fig. 1, a bolus injection of ACh in the mesenteric vascular bed with active tone caused a Drugs sharp decrease in perfusion pressure due to vasodilation, The following drugs were used: ACh chloride (Daiichi Pharmaceutical Co., Tokyo); bradykinin and des-Arg9-[Leu8]-bradykinin (Peptide Institute, Osaka); guanethidine sulphate and indomethacin (Sigma Chemi- cal Co., St. Louis, MO, USA); FR172357 (3-bromo- 8-[2,6-dichloro-3-[N-[(E)-4-(N,N-dimethylcarbamoyl) cinnamidoacetyl]-N-methylamino]benzyloxy]-2-metyl-

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