Changes in L-arginine/nitric oxide pathway of the aorta in septic shock rats

AIM:To observe the change of nitric oxide (NO) generation system in the vascular adventitia, media and intima in septic shock rats.METHODS:The septic shock model was made in rats by caecal ligation and puncture. The intima, media and adventitia of the rat aorta were separated. NO production (NO₂^-), nitric oxide synthase(NOS) activity and L-arginine (L-Arg) transport were measured, separately. Inducible NOS (iNOS) distribution was detected by immunohistochemistry.RESULTS:Both in early and late stage of septic shock, NO₂^- from the intima was decreased by 66.1% and 78.9%(P<0.01), while NO₂^- from the media was increased by 1.1 and 2.2 folds(P＜0.01), and the adventitia 9.6 and 18.6-fold (P＜0.01), as compared with the sham group, respectively. The changes of NOS activity and the L-arginine transport in the intima, the media layer and the adventitia of the aorta in the septic shock rat paralleled with that of NO₂^- in these tissues. The results of iNOS immunohistochemistry showed that there were obviously positive staining in the media layer and adventitia, especially the adventitia of the rat aortas in septic shock, as compared with that in the sham control.CONCLUSIONS:During septic shock, NO production in the aortic intima was progressively suppressed. However, it was progressively increased in the aortic medial layer and adventitia, especially the adventitia with shock processes. These changes result from different changes of L-arginine transport, NOS activity and its expression in three layers of the aorta from the septic shock rat.