诱导型一氧化氮合成酶在迟发性血管痉挛中的作用

Role of inducible nitric oxide synthase in chronic cerebral vasospasm

目的 以大鼠迟发性脑血管痉挛模型为基础研究诱导型一氧化氮合成酶 (iNOS)在迟发性血管痉挛发展中的作用。方法 3 2只雄性SD大鼠随机分为实验组和对照组 ,实验组枕大池二次注血诱导迟发性脑血管痉挛 ,对照组枕大池注射生理盐水。第 8天行脑血管造影 ,枕大池抽取脑脊液测一氧化氮 (NO)浓度。逆转录 聚合酶链反应 (RT PCR )法和免疫组织化学法测定并评价iNOSmRNA和蛋白质在基底动脉、大脑中动脉和皮质中的表达。结果 颅内动脉血管减影提示对照组颈内动脉颅内段、大脑中动脉 (MCA)明显变细 ,大脑中动脉中段直径 (MD)与镫骨动脉中段直径 (SD)之比衡量大脑中动脉的管径显示实验组MCA管径较对照组MCA管径减少 3 0 %。对照组脑脊液中NO浓度为 (11.70± 2 .62 ) μmol/L ,实验组脑脊液中NO的浓度为(5 5 .67± 12 .84)μmol/L。iNOSmRNA和蛋白质表达于基底动脉、大脑中动脉和皮质 ,其中基底动脉表达最强。 结论 iNOS作为迟发性脑血管痉挛发展中的关键因素参与血管壁的迟发性损伤。

Objective To investigate the role of inducible nitric oxide synthase (iNOS) in the chronic cerebral vasospasm after subarachnoid hemorrhage.Methods Chronic vasospasm was induced in 16 male Sprague-Dawley rats by an injection of autologuous blood (250 microl) into the cisterna magna followed by a second injection 24 h later.A control group of 16 animals was treated with injections of 0.9% sodium chloride solution.At the 8th day after the first cisterna magna injection pressure-controlled digital subtract angiography after retrograde cannulation of the external carotid artery was performed.After the cerebral spinal fluid was obtained from 8 animals of each group for the measurement of the concentration of NO,those animals were perfusion fixed and their brains were removed for immunohistochemical assay of iNOS.At the same time the diameter of middle cerebral arteries (MCA) was measured under a microscope.Other 8 animals of each group were perfused with PBS and their brains were removed for measurement of iNOSmRNA expression by RT-PCR.Results In the angiogram of digital subtract angiography,the intracranial internal carotid artery and MCA of the animals in the experimental group were narrowed and their images were blured.Using MD/SD (the ratio of the diameter of MCA with the diameter of the extracranial stapedial artery) to assess the vasospasm,the value of MD/SD in the experimental group was 0.28±0.03,which was 70 % of the value of MD/SD ( 0.40± 0.09) in the control group.Under optical microscopy,the diameter of MCA in the experimental group was ( 0.30± 0.02) mm,which was 75 % of the diameter of MCA in the control group ( 0.41± 0.02) mm.The concentration of NO in the cerebral spinal fluid in the experimental group was (55.67± 12.84) μmol/L,which was nearly 5 times of that in the control group ( 11.70± 2.62) μmol/L.The iNOS mRNA was expressed in basilar artery,MCA and parenchyma,while there was no iNOSmRNA expression in control group.Immunohistochemical labeling of iNOS was found in endothelial cells,vascular smooth-muscle cells and adventitial cells.Some staining of iNOS was observed in activated microglias,glial networks,and neurons.Conclusion iNOS may play a key role in the vascular delayed injury in the cerebral vasospasm after SAH.