Study On The Relationship Between Asymmetric Dimethylarginine And Delayed Cerebral Vasospasm Secondary To Subarachnoid Hemorrhage

Objective: Delayed cerebral vasospasm(CVS) is the pathologiccontraction of cerebral vessels which were stimulated by thecatabolite,oxidation product of clot in subarachnoid space after subarachnoidhemorrhage(SAH). Asymmetric dimethylarginine(ADMA),a homolog ofL-arginine and a competitive inhibitor of nitric oxide synthase(NOS), canaggravate cerebral vasospasm by competitively restrain NOS and reducethe level of Nitric Oxide(NO, an vasorelaxant substance). Thesynthetize and decomposition of ADMA were affected by thecatabolite,oxidation product of clot in subarachnoid space. In this study, theauthors sought to determine whether ADMA levels are associated with CVSand NO in a rat model of SAH.Methods: 78 healthy male adult Sprague-Dawley rats were randomlyallocated into control group(n=6),sham group(n=36) and SAH group(n=36).Rats in sham group and SAH group were respectively further divided into 6subgroup(1d,3d,5d,7d,10d,14d) randomly. Rats in control group were fed fortwo weeks without any intervention and were executed on the fourteenth day;Rats in SAH group were operated to induct a SAH model by doubleautologous blood injection into cisterna magna while rats in sham group wereinjected with normal saline. Arterial blood,cerebrospinal fluid and brainsamples of each group were collected at the preconcerted time. ADMA levelin the plasma and CSF samples were assessed using enzyme-linked immuno sorbent assay(ELISA); Nitrite and nitrate concentration was used as a markerof nitric oxide production in plasma and CSF samples and was determined bynitrate reductase method; Pathomorphological change was observed withoptical microscope, Diameter and thickness of basilar artery was measured byMicrometer after hematoxylin-eosin staining was performed.All data were type-in with microsoft office excel 2003 and wereanalyzed with SPSS 16.0. Results of measurement were presented as meanvalues±SD. Normality test and F test were performed first. Independentsample T-test,one way analysis of variance(ANOVA) and SNK-q test wereused for comparison between or among groups. The Pearson correlationcoefficient was used to assess the correlation between the level of ADMA orNO in the CSF and plasma with the amount of CVS. Statistical significancewas defined as a probability value less than 0.05.Results:1. ADMA levels in CSF were unchanged among 6 subgroups of shamgroup(F=0.107,P=0.99); In the SAH group, ADMA levels in CSF weresignificantly increased in subgroup 1d,3d,5d and 7d compared with shamgroup(P<0.05). In subgroup 10d and 14d,ADMA levels decreased to the levelof sham group(P>0.05).2. NO levels in CSF were unchanged among 6 subgroups of shamgroup(F=0.584,P=0.712); In the SAH group, NO levels in CSF weresignificantly decreased in subgroup 3d,5d and 7d compared with shamgroup(P<0.01). In subgroup 10d and 14d,NO levels increased to the level ofsham group(P>0.05).3. Diameter of BA were unchanged among 6 subgroups of shamgroup(F=0.209,P=0.956); In the SAH group, diameter of BA were significantly decreased in subgroup 1d,3d,5d and 7d compared with shamgroup(P<0.001). In subgroup 10d and 14d, diameter of BA increased to thelevel of sham group(P>0.05); Thickness of BA were unchanged among 6subgroups of sham group(F=0.86,P=0.519); In the SAH group,Thickness ofBA were significantly increased in subgroup 3d,5d and 7d compared withsham group(P<0.05). In subgroup 10d and 14d,Thickness of BA decreased tothe level of sham group(P>0.05).4. No CVS was observed in sham group and control group. In the SAHgroup, Morphological change of BA begun in subgroup 1d and the worst CVSwas observed in subgroup 5d. Microscopic findings showed that endothelialcells were metamorphic and swollen, the chromatin in cell was asymmetricaland the cytoplasm was diffuse vacuous. Medial membrane of BA wasincrassated and internal elastic lamina was circuitous, crapy and evenfractured. Smooth muscle cell of spastic vessel were diminished anddisarranged.5. The ratio of thickness and diameter of BA was used to indicate thedegree of CVS. The level of ADMA in CSF in SAH group was stronglycorrelated with the degree of CVS(r=0.641,P<0.001);NO levels in the CSFwas negatively correlated with ADMA levels in CSF(r=-0.687,P<0.001).6. Plasma ADMA levels in sham group and SAH group were similar andremained essentially unchanged during the several days after SAH(shamgroup:F=0.667,P=0.652; SAH group:F=0.352,P=0.877).7. plasma NO levels were unchanged among 6 subgroups of shamgroup(F=0.346,P=0.881); In the SAH group, NO levels were significantlydecreased in subgroup1d,3d,5d,7d and 10d compared with shamgroup(P<0.01). In subgroup 14d,NO levels increased to the level of sham group(P>0.05).8. Plasma ADMA levels neither correlated with NO levels(r=0.019，P=0.914) nor with the degree of vasospasm(r=-0.046，P=0.791).Conclusions:1. The concentration of CSF NO after SAH decrease gradually and thechange rule of NO is accordance with the progress of CVS.2. The level of ADMA in CSF after SAH increase gradually and it wasstrongly correlated with the degree of CVS.3. Asymmetric dimethylarginine reduce the level of nitric oxide in CSFby inhibit nitric oxide synthase and is involved in the progress of cerebralvasospasm in subarachnoid hemorrhage rats.4. There is no evident correlation between the level of ADMA in plasmaand the degree of CVS.