Effect Of Valsartan On Expresion Of Renal Aquaporin-1,2,5 In Spontaneously Hypertensive Rats

Objective: The present study was aimed to observe the effect of valsartan on blood pressure of spontaneously hypertensive rats(SHR),to detect the expression of m RNA and protein of renal aquaporin-1,2,5(AQP1,AQP2,AQP5)in rats.Provide a new theoretical basis for pharmacodynamic mechanism about treatment of valsartan on hypertension,and new potential targets for development of antihypertensive drugs.Methods: Twelve SHR and twelve Wistar Kyoto(WKY)rats were randomly divided into valsartan group(SHR-V and WKY-V)and normal saline group(SHR-N,and WKY-N),with 6 rats in each group.Valsartan group received drug 10mg(kg·day).Normal saline group fed the converted corresponding volume without valsartan per day.The dosage was modulated weekly based on weight.The systolic blood pressure(SBP)of rat's tail was measured once a week with noninvasive blood pressure instrument.After 40 weeks,blood and kidneys were collected from aorta abdominalis and enterocoelia separately.Angiotensin ? and arginine vasopressin in plasma were measured by chemiluminescence and elisa respectively.Hematoxylin-eosin(HE)staining was used to observe changes of renal morphology in rats.The m RNA and protein of AQP1,2,5 in kidney were examined by real-time quantitative polymerase chain and western blot separately.The expression and localization of AQP1,2,5 protein in kidney were analyzed and observed by immunohistochemistry.Results: 1.The SBP values of SHR were significantly higher than that of WKY rats at 12 th week when beginning of intragastric administration.To 16 th week,the SBP of SHR-V group was significantly lower than that of SHR-N group(P < 0.05).To 40 th week,the SBP decreased furtherly,but it was still significantly higher than that of WKY-N group and WKY-V group,while,there was no significant difference between the WKY-N group and the WKY-V group(P > 0.05).2.At 40 th week,the level of plasma Ang? in SHR-V and WKY-V group were significantly higher compared with SHR-N and WKY-N group separately(P < 0.05).SHR-N and SHR-V group were slightly elevated,but no significant statistical significance compared with WKY-N and WKY-V group separately.The level of plasma AVP in SHR-V group was significantly lower than that of SHR-N group(P < 0.05).The WKY-V group was significantly higher than the WKY-N group(P < 0.05),while the SHR-N and SHR-V group were significantly lower compared with SHR-V and WKY-V group separately(P < 0.05).3.At 40 th week,the results of HE staining showed that,in WKY-N group and WKY-V group,the glomerular capillary wall is thin.The basement membrane was thicker.Tubular brush border and capsular space were clearly visible.In SHR-N group,some glomerulus were hypertrophy.Renal tubular lumen expanded.Partial glomerulus have been atrophied and showed lobulated in shape.Capillary structure is not clear.Mesangial cells and matrix were hyperplasia.Renal tubular interstitial increased and luminal narrowing.The lesions in SHR-V group were significantly reduced.4.At 40 th week,the relative expression of renal AQP1,2,5 m RNA in SHR-V group were all increased compared with SHR-N group(P < 0.05).There was no significant change between the WKY-V group and the WKY-N group(P > 0.05).In SHR-N group,the AQP1,5 were lowered but the AQP2 was increased compared with WKY-N group(P < 0.05).In SHR-V group,there was no significant change of AQP1,5(P > 0.05)but significantly higher AQP2(P < 0.05)compared with WKY-V group.5.At 40 th week,the renal relative gray value of the AQP1,2,5 protein from Western blot showed in SHR-V group was all significantly higher than the SHR-N group(P < 0.05).While there were no significant changes between the WKY-V group and the WKY-N group(P > 0.05).In SHR-N group,the protein of AQP1,5 was lowered(P < 0.05)while the AQP2 protein was no significant change(P > 0.05)compared with WKY-N group.SHR-V group compared with WKY-V group,there were all no significant changes of protein(P > 0.05).6.At 40 th week,the renal results of IHC showed that AQP1 is mainly localized in proximal tubules in cortex and thin descending limb of henle in medulla.The cortex density mean of AQP1 in WKY-N group was significantly higher than medulla(P < 0.05).The cortex in WKY-V group and SHR-V group was significantly lower than medulla(P < 0.05).SHR-N group was no significant difference between cortex and medulla(P > 0.05).AQP2 is mainly expressed in the connecting tubule and collecting duct in cortex,while in medulla it is mainly expressed in collecting duct.The cortex density mean of AQP2 in WKY-N,WKY-V,SHR-N and SHR-V group was all significantly lower than medulla(P < 0.05).AQP5 is mainly expressed in the kidney distal tubule in cortex and medulla.The cortex density mean of AQP5 in WKY-N,WKY-V,SHR-N and SHR-V group was all significantly lower than medulla(P < 0.05).Conclusions: 1.Local RAS was more active in the kidney,and the humoral regulation effect of AVP was relatively enhanced in the later stage of spontaneous hypertension.This effect can be further enhanced by valsartan.2.The renal AQP1 of rats can be redistributed between cortex and medulla in the long-term changes of blood pressure.The average distribution between cortex and medulla of SHR can be changed by valsartan,to that the expression increased in medulla.3.The distribution of AQP2 in renal cortex was lower than that in medulla.The expression of AQP2 m RNA in the kidney of SHR can be increased significantly by valsartan,but the protein increased relatively modestly.4.The distribution of AQP5 in renal cortex was lower than medulla.The expression of AQP5 m RNA and protein in kidney of SHR can be significantly increased by valsartan.