Immunohistochemical expression of intrarenal renin angiotensin system components in response to tempol in rats fed a high salt diet

摘要

AIM To determine the effect of tempol in normal rats fed high salt on arterial pressure and the balance between antagonist components of the renal renin-angiotensin system.METHODS Sprague-Dawley rats were fed with 8% Na Cl highsalt(HS) or 0.4% Na Cl(normal-salt,NS) diet for 3 wk,with or without tempol(T)(1 mmol/L,administered in drinking water). Mean arterial pressure(MAP),glomerularfiltration rate(GFR),and urinary sodium excretion(UVNa) were measured. We evaluated angiotensin Ⅱ(Ang Ⅱ),angiotensin 1-7(Ang 1-7),angiotensin converting enzyme 2(ACE2),mas receptor(Mas R),angiotensin type 1 receptor(AT1R) and angiotensin type 2 receptor(AT2R) in renal tissues by immunohistochemistry.RESULTS The intake of high sodium produced a slight but significant increase in MAP and differentially regulated components of the renal renin-angiotensin system(RAS). This included an increase in Ang Ⅱ and AT1 R,and decrease in ACE-2 staining intensity using immunohistochemistry. Antioxidant supplementation with tempol increased natriuresis and GFR,prevented changes in blood pressure and reversed the imbalance of renal RAS components. This includes a decrease in Ang Ⅱ and AT1 R,as increase in AT2,ACE2,Ang(1-7) and Mas R staining intensity using immunohistochemistry. In addition,the natriuretic effects of tempol were observed in NS-T group,which showed an increased staining intensity of AT2,ACE2,Ang(1-7) and Mas R.CONCLUSION These findings suggest that a high salt diet leads to changes in the homeostasis and balance between opposing components of the renal RAS in hypertension to favour an increase in Ang Ⅱ. Chronic antioxidant supplementation can modulate the balance between the natriuretic and antinatriuretic components of the renal RAS.