Effect Of Common Antihypertensive Drugs On Platelet Activation In Sinoaortic Denerva-Tion Rats

BackgroundIn the Chinese disease spectrum, cardiovascular diseases have been the leading causeof death, and hypertension is the first element of danger. There exists platelet activation inhypertension, and the platelets activation is one of the risks factors of ischemic target organdamage. The previous studies have shown that blood pressure variability（BPV） increasesin hypertension, and high BPV can increase platelet activation. But it is unclear whetherantihypertensive drugs can affect the platelet activation induced by high BPV.AimsDetermine the influence of common antihypertensive drugs on platelet activationcaused by high BPV.Methods1．In vivo experiments: SAD model were performed in SD rats, and divided into shamoperation (Sham) group, SAD group, atenolol group (20mg·kg-1·d-1), captopril group(100mg·kg-1·d-1), nifedipine group (3.0mg·kg-1·d-1) and hydrochlorothiazide group(40mg·kg-1·d-1).Four weeks Four weeks after the operation, blood pressure (BP) and BPVof rats were monitored in freely moving state. Animals were orally administeredabove-mentioned drugs or solvent daily for7consecutive days. Platelet aggregation wasmeasured by turbidimetry method. The perfusion chamber was used to detect plateletadhesion to collagen at the high (1200s-1) and low (300s-1) shear rate. Expression ofP-selection, reactive oxygen species (ROS) and calcium (Ca2+) mean fluorescence intensitywere determined with flow cytometry assay. TXB2was measured with RIA2. In vitro experiments: Blood from Sham-operated rats act as sham group weredivided into SAD group,captoptil group and atenolol group. After incubating withabove-mentioned drugs or solvent at37℃for20min, platelet aggregation, adhesion tocollagen, ROS,Ca2+and TXB2levels were detected with the above methods. 3. In vitro fluctuations experiments: Heparin blood from SD rats randomly dividedinto: normal fluctuating group, fluctuating group, atenolol group and captopril group. Afterincubating with above-mentioned drugs or solvent at37℃for20min, blood was put intothe pressure fluctuation model for5min. Then platelet micro-aggregation was measuredwith flow cytometry assay, and adhesion to collagen, ROS and Ca2+levels were detectedwith the above methods.Results1. The hemodynamic changesIn vivo experiment, there was no significant difference in SBP,DBP and MBPbetween SAD and Sham group. But compared with Sham group, SBPV,DBPV andMBPVsignificantly increase in SAD rats.2. Platelet function changes in SAD rats and in vitro fluctuations modelIn vivo experiment, compared with Sham group, platelet aggregation rate,adhesionrate, the positive expression rate of P-selection,the levels of platelet ROS,NO,Ca2+andTXB2level significantly increased in SAD group Adhesion at high and low shear rate waspositively correlated with the expression rate of P-selection and TXB2level while adhesionat high shear rate was positively correlated with platelet ROS level.In vitro experiment, compared with Sham group, platelet aggregation rate,adhesionrate, the positive expression rate of P-selection,the levels of platelet ROS and Ca2+significantly increased in SAD group. Platelet aggregation induced by ADP (300mol/L)was positively correlated with the expression rate of P-selection, levels of ROS and TXB2.Also the platelet adhesion rate has a positive correlation with the expression rate ofP-selection and levels of ROS and TXB2.The vitro fluctuation experiment results shows that, compared with normal fluctuatinggroup, the platelet adhesion rate, the positive expression rate of P-selection and Ca2+levelsignificantly increased in fluctuating group.Adhesion at low shear rate has a positivecorrelation with the positive expression rate of P-selection.3. Effects of common antihypertensive drugs on platelet activation induced by highBPVThe vivo experiment results showed that, compared with SAD group, ADP andcollagen induced platelet aggregation, the platelet adhesion rate，the positive expressionrate of P-selection, levels of ROS, NO and Ca2+in platelet significantly decreased inatonally group, captoptil group,nifedipine group and hydrochlorothiazide group. similarly,the vitro experiment results showed that, compared with SAD group, platelet aggregation, the platelet adhesion rate, the positive expression rate of P-selection, levels of Ca2+inplatelet significantly decreased in atenolol group and captoptil group. In vitro fluctuationexperiment results showed that, compared with fluctuating group, the platelet adhesion rate,the positive expression rate of P-selection and level of Ca2+in platelet significantlydecreased in atenolol group and captoptil group.ConclusionsFour kinds of antihypertensive drugs have inhibitory effects on platelet activation inhigh BPV state. These effects might be related to the increased level of Ca2+in platelet.