Effects Of Particulate Matter(PM_2.5) On Isolated Rat Thoracic Arota And The Possbile Mechanisms

ObjectiveTo study the mechanisms of PM_2.5 on isolated rat thoracic aorta by means of the observation of PM_2.5 and the combinations of PM_2.5 with endothelium, N-nitro-L-arginine methylester (L-NAME) ,SOD on PE-contracted and Ach or SNP-relaxated aorta rings.MethodsThe isolated thoracic aorta ,removed from 220-270g male wister rats, was cut into3-4mm.The vascular rings were mouted in stabdard muscle baths,isometric tension of the vascular rings was measured.we observed:(1)Expose the vascular rings to PM_2.5 with cumulative concentrations.(2)Effect of PM_2.5 on the contraction of the aorta(with and without endothelium) induced by phenylephrine(PE) with or without SOD and L-NAME.(3)Effect of PM_2.5 on the relaxation of the aorta induced by acetylcholine(ACh) or Sodium Nitroprusside(SNP) with or without superoxide dismutase(SOD).Results(1)PM_2.5 did not directly cause any relaxation or contraction responses in vascular rings(P>0.05).(2)PM_2.5 significantly enhanced the contraction of the vascular rings with endothelium induced by phenylephrine (except 10-9mol/l), the enhance showed a concentration-dependent positive correlation(P<0.01) and did not effect on the vascular rings without endothelium for the same concentration of PM_2.5(P>0.05).PE(10-5mol/l)-induced contraction was increased by 5.83%(PM_2.5 10μg/ml,P<0.01) and by 26% (PM_2.5 100μg/ml,P<0.001). Pretreatment with L-NAME enhanced the effect of PM_2.5 ,but SOD completely abolished this effect of PM_2.5 at a concentration of 20u/ml.(3)PM_2.5 markedly inhibited the relaxation of the aorta induced by Ach (except 10-9mol/l),but not by SNP.The inhibition showed a concentration-dependent positive correlation(P<0.01).Ach (10-5mol/l)-induced relaxation was reduced by 21% (PM_2.5 10μg/ml,P<0.01)and 47.25%(PM_2.5 100μg/ml,P<0.001).SOD completely abolished the inhibitory effect of PM_2.5.Conclusions(1)PM_2.5 did not directly cause any relaxation or contraction in vascular rings. (2)PM_2.5 significantly enhanced the contraction of thoracic aorta rings with intact endothelium induced by phenylephrine.The effect showed concentration-dependent positive correlation,and these is difference in the enhance between the vascular rings with and without endothelium for the same concentration of PM_2.5 .(3)PM_2.5 significantly reduced the relaxation of the vascular rings with endothelium induced by acetylcholine.(4)SOD reduce the effects of PM_2.5 .(5)PM_2.5 impaired endothelium through oxidative stress.(6)The effect of PM_2.5 on the aortic rings of rats has business with NO.