The Study Of The Vasorelaxant Effect Of Oxytocin On Isolated Rat Thoracic Aortic Ring And Its Possible Mechanism

ObjectiveTo study the vasorelaxant effect of OT on pregnant and non-pregnantrat rats'isolated pre-contracted by phenylephrine (PE) thoracic aortic rings and its relaxation mechanismsMethodsThe tension of isolated thoracic aortic rings from rat was measured by tissue organ bath system. To study vasorelaxant effect of OT on the precontracted by phenylephrine (PE) rat aortic rings with or without endothelium. Nitric oxide synthase inhibitor Nitroso-L-arginine methyl ester (L-NAME) cyclooxygenase inhibitor indomethacin (Indo) and K+ channel blockerswere applied before aortic rings exposed to OT. CaCl2 was been adding cumulatively to inendothelium-denuded aortic rings after pre-contracted by phenylephrine (PE) and pretreated in Ca2+ free K-H solution with 3.2u OT. Results OT can not relax pre-contracted by phenylephrine(PE) non-pregnant rats'isolated aortic rings. But OT(0.1U-3.2U) can concentration-dependent relax pre-contracted by phenylephrine(PE) with or without endothelium pregnant rats'aortic rings. The Nitric oxide synthase inhibitor nitro–L–argininemethy lester Asia(L-NAME) inhibited the vasorelaxant effect of OT on the pre-contracted by phenylephrine(PE) pregnant rats'isolated aortic ring. Cyclooxygenase inhibitor indomethacin (Indo) had no effect on pre-contracted by pheny-lephrine(PE) rats'isolated aortic rings'tension.Non-selective K+ channel blocker (TEA) 3mmol/L can weaken the OT'vasorelaxation effect on the pre-contracted by phenylephrine(PE) arterial rings. Vasorelaxation effect of OT has no observed effects with the Ca2+ concentration.ConclusionOT has no effect on tension of pre-contracted by phenylephrine(PE) non-pregnant rats'isolated aortic rings; OT has concentration-dependent vasorelaxation effect on pre-contracted by phenylephrine (PE) with or without endothelium pregnant rats'arterial rings .The mechanism is through promoted the sensitivity of Nitric oxide synthase and open of K+ channels.