Effects Of Losartan On Expression Of NHE3 In Renal Tubule And Renal Protection Of Spontaneously Hypertensive Rats

PARTⅠEffect of Losartan on Expression of NHE3 in Renal Tubule of Spontaneously Hypertensive Ratsobjective:The present study was designed to observe effect of Losartan on expression of Sodium hydrogen exchanger isform 3(NHE3) in Renal Tubule of Spontaneously Hypertensive Rats and the expression changes of Serum and glucocorticoid inducible kinase 1(SGK1).To explore Losartan exert its role whether it is mediated through SGK1 expression. As we may obtain some new clues about pharmacodynamics mechanisms of Losartan in hypertension,or provide new action targets for antihypertensive drugs. Methods:Twelve Spontaneously Hypertensive Rats were divided randomly into untreated group(SHR group) and treated group with Losartan(Los group) (6 rats in each group),six Wistar Kyoto rats were set as normal control(WKY group). Los group received drugs 30mg/kg/day and the drugs were distilled solvent.WKY group and normal SHR group fed the same volume of solvent per day. Modulate the dosage according to weekly weight. Systolic blood pressure (SBP) was measured by tail-cuff every two weeks. After 8 weeks, AngiotensinⅡin serum and renal tissue were measured by Radioimmunoassay. The mRNA of NHE3 and SGK1 in renal tubule have been examined by real-time polymerase chain reaction. One kidney of each rat was as a source for evaluating the expression and location of NHE3 protein using immunohistochemistry peroxidase ligation method and image analysis method. Results:1. Systolic blood pressure (SBP) of SHR group was significantly higher than WKY group (P<0.05);when Los group fed with Losartan(30mg/kg/day) two weeks, SBP of Los group was significantly lower than SHR group which fed with solvent (P<0.05);SBP continuely reduced significantly during the next 6 weeks;2. After 8 weeks treatment, the level of serum AngiotensinⅡin Los group were significantly higher than WKY group (P<0.05), but compare with SHR group,there was no significant difference(P>0.05);the level of renal tissue AngiotensinⅡin Los group were significantly higher than WKY group (P<0.05), but compare with SHR group,there was no significant difference (P>0.05); 3.The mRNA expression levels of NHE3 in renal tubule of SHR group,estimated by Real-time quantitative PCR, were increased 2.3 folds than WKY group, while Los group has increased 1.65 folds; 4.The expression level of NHE3 protein in renal tubule, estimated by immunohistochemistry method, was increased in SHR group and differences were obvious when compared with WKY group. Radioimmuno assay revealed that the lever of NHE3 protein in renal tubule, increased significantly in SHR group.5,The mRNA expression levels of SGK1 in renal tubule of SHR group, estimated by Real-time quantitative PCR, were increased 3.31 folds than WKY group, while Los group has increased 1.84 folds. Conclusion:1,The RAS in serum and renal tissue of Spontaneously hypertensive rats were activated generally and the activation of RAS can not been inhibited by Losartan.2,The overexpression expression of NHE3 mRNA and protein in renal tubule of Spontaneously hypertensive rats were probable correlated with AT1 recepter activation.3,The overexpression expression of SGK1 mRNA in renal tubule of Spontaneously hypertensive rats mediated by AT1 receptor,this may be an intermediate which lead the overexpression of NHE3; 4,Effect of Losartan on pharmacodynamic mechanisms of hypertension may correlated with the restriction of overexpression of SGKland NHE3.5,The overexpression expression of SGK1 and NHE3 mRNA in renal tubule of Spontaneously hypertensive rats inhibited by Losartan was in consistent with the antihypertensive efficacy. PARTⅡEffect of Losartan on Oxidative Stress and Renal Function in Spontaneously Hypertensive Ratsobjective:The present study was designed to observe effect of Losartan on Oxidative Stress and Renal Function in the Spontaneously hypertensive rats, to explore the protection mechanisms of renal damage in the Spontaneously hypertensive rats. Methods:Twelve Spontaneously Hypertensive Rats were divided randomly into untreated group(SHR group) and treated group with Losartan(Los group) (6 rats in each group),six Wistar Kyoto rats were set as normal control(WKY group). Los group received drugs 30mg/kg/day and the drugs were distilled solvent.WKY group and normal SHR group fed the same volume of solvent per day. Modulate the dosage according to weekly weight. After 8 weeks, One kidney of each rat was as a source for evaluating the renal pathological changes using Hematoxylin and eosin staining(HE).The level ofβ2-microglobulin (β2-MG) in urine was measured by radioimmunoassay. The activites of serum and renal tissue Nitric oxide(NO),Superoxide dismutase(SOD)and Maleic dialdehyde (MDA)were detected with chromatometry; The content of serum Serum creatinine (SCr) and Blood urea nitrogen(BUN) were detected with chromatometry. Results:1. At 18 weeks, the activites of serum and renal tissue NO,SOD in SHR group were significantly lower than WKY group (P<0.01; P<0.01) while the Los group increased significantly compare with SHR group (P<0.05;P<0.05). The activite of serum and renal tissue MDA in SHR group were significantly higher than WKY group (P<0.01) while the Los group decreased significantly compare with WKY group (P<0.05); 2.No significant difference was found in the study such as SCr in serum (P>0.05) but the level of BUN in serum andβ2-MG in urine increased obviously while the Los group decreased significantly respectively (P<0.05; P<0.01).Conclusion:1. Oxidative Stress probably participate in the pathogenesis of hypertensive nephrosclerosis; 2.Losartan possible have a certain protective effect on hypertensive nephrosclerosis Renal protective mechism of Losartan may be, at least partly, correlated with improving the Oxidative stress.