| Background and ObjectivesIt was important to preserve renal function for delaying the progress of chronic heart failure (CHF). Epidemiology showed that mild renal hypofunction was a risk factor of poor prognosis of CHF. In recent years, the interaction between heart and renal in CHF patients has been widely paid close attention. It was indicated that there was renal dysfunction characteristic of damaged glomerular filtration and impaired baroreflex in CHF patients. Thus, it is significant to study the effect of renal hypofunction on the advancement of CHF.Now, levels of creatinine and urea nitrogen in serum as conventional biochemical indicators have been used to evaluate renal function clinically, but they were affected by such factors as muscle, diet and some morbid states and were above normal values only when renal function was seriously damaged, so they could not be used to diagnose early renal hypofunction in CHF patients. Levels of cystatin(CysC)in serum and microamount albumn(MA),β2-microglobulin(β2-MG), N-acetyl-β-glucosaminidase(NAG), aquaporin -2(AQP-2) in urine were seldomly influenced by various kinds of factors and began to change at an early stage of renal hypofunction, so they have already been used as early renal hypofunction biochemical indicators in clinical and experimental research. Concentration of cysC in serum was completely determined by glomerular filtration rate. MA leaking out to urine increased when glomerular filtration barrier damaged resulting from some factors, such as inflammation, immunologic injury. The levels ofβ2-MG,NAG in urine increased when nephric tubule damaged and its reabsorption was lesioned. Level of AQP-2 of kidney directely affected water reabsorption and a part of AQP-2 ablating to nephric tubule lumens was flushed by urine, so the level of AQP-2 in urine might indirectly reflected renal function. Level of endothelinin-1(ET-1) in serum seriously influenced hemodynamics states which positively correlated with renal function, so, we measured level of ET-1 in serum of people in two groups too.ET-1, vasoactive peptide constituted of 21 amino acids, was detached and purified from pig arteriae aorta endotheliocyte in 1988. It was found that epithelial cell of medulla interna collecting duct secreted a large amount of endothelin-1 (ET-1) which weakened renal sensitivity to antidiuretic hormone (ADH) and so inhibited water reabsorption and eased heart preload. AQP-2, expressed on cytolemma and intracytoplasm at the side of lumens of principal cell of renal collecting duct, was a main renal aquaporin regulated by arginine vasopressin (AVP). Its expression and shuttling back and forth regulation closely correlated with the collecting duct reabsorption. Therefore, ET-1 and AQP-2 of collecting duct played an important role in maintaining body fluid balance.AngiotensinⅡ(AngⅡ) was a main active compound of renin-angiotonin system and combined with AT1 receptor of such kinds of tissue as vascular smooth muscle, adrenal gland, kidney and heart. It possessed biological effect of vasoconstriction and promoting aldosterone release, so it added heart preload and afterload. Angiotensin receptor blocker (ARB)-losartan potassium combined selectively with AT1 receptor and blocked above adverse effects caused by AngⅡ, thus, it could protect heart and renal function.This experiment was based on research conducted on two levels of clinical patients and animal model, both with ARB-losartan potassium intervention. Mechanism of early renal hypofunction in CHF and the therapy effect of losartan potassium on renal function were explored in this study.Methods1. CHF patients and healthy people in health examination were selected as CHF group and control group respectively. Patients in CHF group were randomly divided into two subgroups of conventional therapy and losartan potassium therapy, both with 8 weeks of drug treatment. Before drug treatment, level of ET-1 in serum and heart contractile function, such as values of left ventricular end-diastolic dimension (LVEDD), left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS) and renal function, such as levels of CREA, UREA, CysC in serum and AQP-2, MA,β2-MG and NAG in urine were measured in both groups. After 8 weeks of drug treatment, above indicators were measured again in two subgroups of CHF group. 2. All mouse were randomly divided into three groups: sham operation group, CHF group and losartan potassium group. The CHF mouse model after acute myocardial infarction (AMI) was set up by ligating left anterior descending coronary artery, while left anterior descending coronary artery was not ligated, but was through in sham operation group. Before operation and 2 weeks after operation, hemodynamics indicators, such as values of left ventricular end-diastolic pressure (LVEDP), left ventricular end-systolic pressure (LVESP), left ventricular pressure max upstroke/downstroke velocity(±dp/dtmax) were measured in three groups. Significances of above indexes were regarded as a signal of successful CHF model. CHF mouse were randomly divided into CHF group and losartan potassium group. After 2 weeks of operation, 1.5ml water was given by intragastric administration in sham operation group and CHF group. 1.5ml 0.2% losartan potassium was given by intragastric administration in losartan potassium group. All administration was once a day and with 8 weeks. 10 weeks after operation, above hemodynamics indicators were measured again and additional following indicators were detected: (1) Expressions of AQP-2mRNA, ET-1mRNA of mouse renal tissue were detected with reverse transcription polymerase chain reaction (RT-PCR); (2) Expressions and distribution of protein of AQP-2 and ET-1 of mouse renal tissue were detected with immunohistochemical method;(3) Expressions of protein of AQP-2 and ET-1 of mouse renal tissue were detected with western blot.Result1. Before treatment, the value of LVEDD increased significantly and the values of LVEF and LVFS decreased notably in CHF group compared with control group. The value of LVEDD was much lower and the values of LVEF and LVFS were much higher after 8 weeks of drug treatment than before treatment in two subgroups of CHF group respectively. There were no significances of the values of all above indictors between two subsets of CHF group before treatment, but after 8 weeks of drug treatment, the value of LVEDD was much lower and the values of LVEF and LVFS were much higher in losartan potassium group than in conventional therapy group.2. The levels of CREA and UREA in serum and NAG,β2-MG in urine were in ranges of normal values in control group and CHF group before treatment. 3. Before treatment, the levels of CysC,ET-1 in serum and MA, AQP-2 in urine increased significantly in CHF group compared with control group. The levels of above biochemical indicators were much lower after 8 weeks of drug treatment than before treatment in two subgroups of CHF group respectively. There were no significances of the levels of these detection indexes between two subgroups of CHF group before treatment, but after 8 weeks of drug treatment, the levels of these indictors were much lower in losartan potassium group than in conventional therapy group.4. There were no significances of all hemodynamics indexes of mouse between before operation and 2 weeks of operation in sham operation group, but the value of LVEDP increased significantly and the values of LVESP and±dp/dt max decreased notably after 2 weeks of operation than before operation in CHF group and losartan potassium group.5. After 10 weeks of operation, compared with in sham operation group, the value of LVEDP increased significantly in CHF and the value of it was much lower in losartan potassium group than in CHF group, but was still much higher than in sham operation group; the values of LVESP,±dp/dt max decreased significantly in CHF and the values of them were much higher in losartan potassium group than in CHF group, but were still much lower than in sham operation group.6. After HE stain, there was no obviously pathological structure change of renal glomeruli of mouse in three groups. Normal structure of renal tubule was observed in sham operation. There was vacuolization of renal tubule in CHF group and the pathological change of renal tubule in losartan potassium group eased, but there were still changes of oedema and degeneration under light microscope.7. Compared with in sham operation group, the expressions of AQP-2 mRNA and AQP-2 protein of mouse renal tissue increased significantly in CHF group. The expressions were much lower in losartan potassium group than in CHF group, but were still much higher than in sham operation group.8. After immunohistochemistry stain, positive expression of AQP-2 protein of mouse renal tissue, presented with buffy grains, mainly distributed in epithelial cells of collecting tube under light microscope. There was light amber-coloured stain in mouse renal tissue in sham operation group and there was obviously augmented stain in CHF group. There was lighter colored stain in losartan potassium group than in CHF group, but was still much deeper than in sham operation group.9. Compared with in sham operation group, the expressions of ET-1 mRNA and ET-1 protein of mouse renal tissue increased significantly in CHF group. The expressions were much higher in losartan potassium group than with in CHF group too.10. After immunohistochemistry stain, positive expression of ET-1 protein of mouse renal tissue, presented with buffy grains, mainly distributed in renal glomeruli and epithelial cells of collecting tube under light microscope. There was light amber-coloured stain in sham operation group and there was obviously augmented stain in CHF group compared with in sham operation group. There was also much deeper in losartan potassium than in CHF group.Conclusions1. The levels of CysC in serum and MA, AQP-2 in urine increased significantly, showing that there was early renal hypofunction characteristic of glomerular filtration functional lesion in CHF patients.2. The levels of NAG,β2-MG in urine were in ranges of normal values, showing that there was normal tubular reabsorption function in CHF patients.3. Such common biochemical indicators as the levels of CREA,UREA in serum had no diagnostic function, while combined measurement of the levels of such early renal function biochemical indicators as the levels of CysC in serum and MA, AQP-2 in urine had diagnostic value for early renal hypofuncion in CHF patients.4. The level of ET-1 in serum increased significantly, showing that there was obviously hemodynaics change in CHF patients.5. The increasing gene and protein expressions of renal AQP-2 of CHF mouse promoted collecting duct to reabsorb water; while the increasing gene and protein expressions of ET-1 of CHF mouse, resulted from increasing volume load, inhibited collecting duct from reabsorbing water.6. Losartan potassium could effectively improve heart systolic function of CHF patients and hemodynamics states of patients and mouse with CHF.7. Losartan potassium could improve glomerular filtrateion function of CHF patients. 8. Losartan potassium could downregulate gene and protein expressions of AQP-2 and upregulate gene and protein expressions of ET-1 of renal tissue of CHF mouse, so it inhibited collecting duct from reabsorbing water and promoted kidney to excrete water and sodium, which maybe a new explanation of its mechanism of action of delaying the course of CHF.
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