Influence Of Different Dietary Salt Concentration On The Expression Of Renal Cortex AQP1, NHE3 And Na⁺/K⁺-ATPase ?₁ In Dahl Salt-Sensitive Rats

Objective:We investigated the effect of different dietary salt concentration on blood pressure of Dahl rats,and detected the expression of mRNA and protein of renal cortex AQP1,NHE3 and Na⁺/K⁺-ATPase?₁ in rats.The present study could provide a new theoretical basis for pathogenesis of the special type hypertension,and produced a new thought to hypertension prevention.Methods:Twenty-one Dahl SS rats and twenty-one Dahl SN rats were randomly divided into salt sensitive group?H-SS,M-SS and L-SS?and non-salt sensitive group?H-SN,M-SN and L-SN?according to 8%NaCl,3%NaCl and 0.3%NaCl concentration,fed for18 weeks with 7 rats in each group.We measured the blood pressure of the tail artery once a week by noninvasive blood pressure instrument.Blood and kidneys were collected from aorta abdominalis and enterocoelia separately.The plasma renin activity,aldosterone,angiotensin II and serum creatinine were measured by ELISA and chemiluminescence respectively.Hematoxylin-eosin?HE?staining was used to observe changes of renal morphology in rats.The mRNA and protein of AQP1,NHE3 and Na⁺/K⁺-ATPase?₁ in renal cortex were examined by real-time quantitative polymerase chain and western blot separately.The expression and localization of AQP1,NHE3 and Na⁺/K⁺-ATPase?₁ protein in kidney were observed by immunohistochemistry.Results:?1?At 9th week,The SBP of rats maintained on high-salt diet was significantly higher than rats fed with middle-salt and low-salt diet?P<0.01?.Meanwhile the SBP of rats in H-SS group was higher than that of in H-SN group?P<0.01?.While 18th week,the SBP of rats fed with high-salt diet was significantly higher than rats fed with middle-salt and low-salt diet?P<0.01?,the SBP of in M-SS group was higher than that of in L-SS group?P<0.01?.Besides,the SBP of Dahl SS was higher as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?2??1?The plasma renin activity was decreased in rats maintained on high-salt and middle-salt diet as compared to rats fed with low-salt diet?P<0.01?.Meanwhile,The plasma renin activity was slightly higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?2?The plasma aldosterone concentration in H-SS and M-SS group were significantly higher than in L-SS groups?P<0.01?,While that of in H-SS group was higher than M-SS group?P<0.01?.There was no significant difference between groups in Dahl SN rats?P>0.05?.Moreover,The plasma aldosterone concentration was higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?3?The plasma Ang?concentration in M-SS group were higher than in L-SS group?P<0.01?,that of in H-SN and M-SN group were lower than in L-SN group?P<0.01?.The plasma Ang?concentration was higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?4?The serum creatinine concentration in rats fed with high-salt and middle-salt diet were higher as compared with rats fed with low-salt diet?P<0.05?,and it was higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?3?The result of HE staining showed that some lesions appeared in rats maintained on high-salt diet.The renal tubular lumen expanded and lumen fusion,increased tubular contents and thinner wall thickness.Renal tubular interstitium increased and fibrosis was evident.The glomerular injury occurred a variety of performance including mesangial expanded,cell hyperplasic,volume expanded and glomerular leaved.The capillary wall was thin and structure was not clear.The lesions in M-SS group was reduced,and there weren't obvious lesions founded in the other groups.?4?The result of renal cortex Western blot and RT-PCR:?1?The lative gray value and the mRNA relative expression of the renal cortex AQP1 protein in H-SS group and M-SS group were all significantly higher than in L-SS group?P<0.01?,and that were lower in H-SN group than in L-SN group?P<0.01?.While the lative gray value and the mRNA relative expression of the renal cortex AQP1 protein were higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?2?The mRNA relative expression of the renal cortex NHE3 protein was lower in H-SN group as compared with L-SN group?P<0.05?,while the lative gray value and the mRNA relative expression of the renal cortex NHE3 were higher in H-SN group than L-SN group?P<0.05?.?3?The renal relative gray value and the mRNA relative expression of the Na⁺/K⁺-ATPase?₁ protein in H-SS group were both significantly higher than in L-SS group?P<0.01?,while just m RNA relative expression was higher in M-SS group as compared with L-SS group?P<0.01?.The renal relative gray value and the mRNA relative expression were both higher in H-SN group than in L-SN group?P<0.01?.Meanwhile,they were higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?5?The result of renal cortex IHC showed:?1?The average optical density value of AQP1 in H-SS and M-SS group were all significantly higher than in L-SS group?P<0.01?,that in H-SN group was lower than in L-SN group?P<0.05?.The average optical density value of AQP1 was higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.?2?The average optical density value of NHE3 in H-SN group was higher than in L-SN group?P<0.01?,while there was no statistical difference between each group of Dahl SS?P>0.05?.?3?The average optical density value of Na⁺/K⁺-ATPase?₁ was higher in H-SS and M-SS groups than that in L-SS group?P<0.01?,and it was higher in H-SS group than in M-SS group?P<0.01?.The average optical density value was higher in H-SN group than L-SN group?P<0.01?.Moreover,the average optical density value of Na⁺/K⁺-ATPase?₁ was higher in Dahl SS rats as compared with Dahl SN rats in high-salt and middle-salt diet?P<0.01?.Conclusions:?1?The sodium dietary stimulated the blood pressure increased both in Dahl SS and Dahl SN rats,which is related to salt dietary concentration and salt sensitivity.?2?High salt dietary reduced the plasma renin activity,increased the level of plasma aldosterone,Ang?and serum creatinine in Dahl SS rats;High salt dietary reduced the plasma renin activity and plasma Ang?level,increased the serum creatinine level in Dahl SN rats.?3?High salt dietary stimulated the expression of renal cortex AQP1 mRNA and protein in Dahl SS rats,but reduced that in Dahl SN.?4?High salt dietary reduced the expression of renal cortex NHE3 mRNA in Dahl SS rats,but increased the expression of NHE3 mRNA and protein in Dahl SN rats.?5?High salt dietary increased the expression of renal cortex Na⁺/K⁺-ATPase?₁ mRNA and protein both in Dahl SS and Dahl SN rats.