Evaluating The Role Of Endothelin-1 In Canine Basilar Arterial Vasospasm By MRI

Objective:Endothelins are 21-amino acid peptides ,can evoke potent dose-dependent long-lasting vasoconstriction. Endothelin-1 is important role in delayed cerebral vasospasm after subarachnoid hemorrhage.The aim of our study was to observe the changing of MR image and morphology after the model was made.We measure the caliber of basilar arteries and endothelin-1 level in plasma and CSF taken from the vasospasm models,which induced by subarachnoid hemorrhage,try to finding the relationship of the caliber of basilar arteries and endothelin-1 level.Furthermore,to definite the role of magenatic resonance imaging in diagnosis vasospasm after subarachnoid hemorrhage. Materials and methods:Nine adult mongrel dogs,each weighting 10 to 15 kg,were sedated with intramuscular ketamine(10mg/kg) followed by intravenous pentobarbital sodium(50mg/kg).9# needle was used to puncture subarachnoid space,collecting CSF(0.5ml/kg),injecting autologous blood which from femoral artery into cisterna magna(0.5ml/kg),then the dog was tailed-up at 30 degree for 30 minutes.MR scan include T1(SE-T1),T2(FSE-T2), FLAIR,DWI,diffusion weighted imaging,3D-TOF-MRA.Scan time was before making model and 2,4,6,8,10,12,14 days after making. Digital subtraction angiography was made when basilar artery vasospasm was finding on MRA image. 5-8 milliliter blood from venous was drawn into tubes containing EDTA ,centrifuged 3000r.p.m 15 minutes.1 milliliter CSF was drawn into tubes containing EDTA.All samples were stored in -70 degree refrigerater until assay. 4 and 14 days after model made,the dogs were sacrificed by intracardiac injection of 4% formaldehydum and the perfusion fixed brian was removed by craniectomy,specimens were selected based on the abnormal manifestations on MR images and stained with HE or immunohistochemistry,finding the changing of intima and internal elastic laminal and smooth muscle after the model were made. Comparing the MR images with DSA finding,we should know the degree and extent of vasospasm and the time that vasospasm occurred.Finding abnormal signal on T1,T2,FLAIR,DWI images.All data were inputed into computer to be analyzed by statistical software SPSS11.0,using same software to test whether there were correlation relationship between MRA finding and ET-1 level. Results:Black color coagulated blood was found around the basilar arteries.Caliber of basilar arteries were reductionand internal elastic laminal were shrinking like zigzag on the 4th day after model made on HE stained slice, many RBC was find around the basilar arteries.The intima of basilar arteries,from the specimen which 4days after model was made, was deep stained on immunohistochemistry staining slices,and the intima from normal basilar arteries and 14 days after the model was made show slight stained on immunohistochemistry staining slices.MRA imaging show the vasospasm of basilar arteries occurred from 2 to 6 days(average4.6day) after the model was made.There were no significant diffrience of ET-1level among each group of plasma and CSF. Conclusion:1.ET-1 should be more a production of ischemia sequelae of vasospasm induced by subarachnoid hemorrhage than a cause of vasospasm after subarachnoid hemorrhage.2.MRI is an important tool of diagnose vasospasm after subarachnoid hemorrhage,for it can provide the degree and extant of vasospasm also can display the early ischemia changing after vasospasm.