Study Of Vascular Elasticity By Echo-tracking Technique In Atherosclerosis Rabbits

IntroductionThe impairment of vascular function has become the important marker of cardiovascular risks, it is a important determinative factor of systolic blood pressure, diastolic blood pressure and pulse pressure. It reflects the endothelial function to some extents. Early atherosclerosis is originated by endothelium disfunction, which continues through the whole process. To detect the correlation between the endothelial function and vascular elasticity, to search the substitutional index of endothelial function , to find the vascular function abnormality exactly, to intervent and treat promply, which is the most important to achieve the first class preventation in the early period of atherosclerosis ,especially before the morphology has changed. In this study we evaluated the endothelial function and vascular elasticity and correlativity, pathological changes during the different feeding time in atherosclerotic rabbits, and assess the effect of simvastatin on the endothelial function , vascular elasticity , the protein expression of inos,enos.Methods1,Six Chinese white big ear rabbits, weighting 2.0-3.0g, were fed with normal diet. The values of femoral elasticity includingβ,EP,AC,PWVβwere measured by linear array transducer with frequency of 13 MHz using echo-tracking technique after infused ACH,GLY,L-NMMA.2,Twenty four Chinese white big ear rabbits, weighting 2.0-3.0g, were randomly divided into four groups ( 6 rabbits one group ) : control group were fed with normal diet, cholesterol diet 4 weeks group,cholesterol diet 8 weeks group,cholesterol diet 12 weeks group fed with 1% cholesterol, 10% egg yellow, 5% greasy a day. The endothelial function, vascular elasticity of aorta and femoral artery were measured by linear array transducer with frequency of 13MHz using ET technique. EDD (endothelial dependent dilation ) = ( D₁-D₀) / D₀×100%, NEDD ( non-endothelial dependent dilation ) = ( D₂ - D₀) / D₀×100%, D₀ is internal diameter of artery at base condition, D₁ is internal diameter of artery after infusing ACH, D₂ is internal diameter of artery after infusing GTN. The parameters of vascular elasticity are the same as the former. The Venous blood of all the rabbits was drawed before execute, Serum TC, TG, HDL, LDL were measured with enzymic method by automatic biochemistry analyzer. At the same time, the arteries were fixed with formalin, sliced, HE stained and observed with electron microscope.3,Fourth-two Chinese white big ear rabbits, weighting 2.0-3.0g, were randomly divided into three groups: control group ( 6 rabbits ) were fed with normal diet, atherosclerosis group ( 6 rabbits ) were fed with 1% cholesterol, 10% egg yellow, 5% greasy a day. Simvastatin group were fed with high cholesterol diet for 4 weeks , then with high cholesterol diet and simvastatin 10mg/kg a day for another 8 weeks. All rabbits were fed 12 weeks. EDD ,NEDD, the index of elasticity were measured with ET technique by high resolution sonography. At the same time blood fat and pathology were detected. The expression of inos, enos was also analyzed by immouno histochemistry with polyclone antibody of anti-rabbit inos, enos using ABC method.Results 1,The blood pressure and heart rate weren't affected after infusing L-NMMA to the proximal and distal end of femoral artery respectively (P>0.05) . The elasticity of femora artery was reduced after infusing L-NMMA to the proximal end of femoral artery compared with basal NO production. (P<0.05) . There was no significant difference of elasticity of femora artery after infusing ACH and L-NMMA compared with basal NO production. (P>0.05) . Significant difference of elasticity of FA was found after infusing GTN and infusing GTN + L-NMMA to the proximal end of femoral artery compared with basal NO production (P<0.05) .2,Serum TC, LDL stepped up and HDL decreased with the progress of arterosclerosis, EDD dysfunction occurred at the 4-th week and NEDD dysfunction occurred at the 12-th week in the cholesterol group , all significantly. The dysfunction of femoral and aorta artery elasticity occurred at the 4-th and the 12-th week and aggravated gradually with the course of disease in the cholesterol group (P<0.05) . EDD measured at the 4-th week in the cholesterol group was correlated to the elasticitic indexs of FA (P<0.05) , but not the AO, however. Pathological changes was obvious at the 8-th week and aggravated gradually at the 12-th week. At the same time, the expression of inos, enos increased obviously.3,In the Simvastatin group, the level of blood fat,EDD,NEDD,the elasticity of FA and AO improved greatly compared with AS group at the 12-th week (P<0.05). At the same time, Pathological changes reduced and the expression of inos, enos decreased obviously compared with AS group.Conclusions1,Basal NO production influences FA distensibility, in addition, exogenous ACH and GTN both increase arterial distensibility, the effect of ACH was mainly from NO.2,EDD damage occurred before NEDD damage, the elasticity impairment of FA occurred before morphology changes, the elasticity impairment of AO occurred after morphology changes, EDD was related to the elasticity of FA, not the AO, however. Therefore, the elasticity of FA may act as the substitutional index of EDD.3,Simvastatin can improve EDD, NEDD, the elasticity of muscular artery and elasticity artery, reduced the expression of inos, enos in the vascular wall, which increased in AS rabbits.