Benefit of vascular decongestion in glycerol-induced acute renal failure

The post insult administration of vascular decongestants has resulted in attenuation of experimental acute renal failure (ARF) following the introduction of various nephrotoxins including drugs, heavy metals, and endotoxin. In the present study, the dose-dependent effects of a novel methylxanthine, HWA-138, were studied in the glycerol-induced murine model of ARF. Renal function, assessed by serial inulin clearances at 24 and 48 h after glycerol injection, urinary electrolyte excretion rates, and renal morphology, was compared between controls and those given glycerol and single i.v. doses of 0.1, 0.5, 1.0, 5.0, and 10.0 mg/kg of HWA-138, or physiologic saline. Whereas significant renal dysfunction was found in all animal groups given glycerol, the mean inulin clearance values of animals given HWA-138 1 mg/kg closely approximated values found in control rats. There were no changes in renal electrolyte excretion rates in animals given HWA-138 compared with relative natriuresis found in untreated glycerol ARF rat. Although a modest decrease in medullary congestion was associated with rats given 1 mg/kg of HWA-138, there was no obvious structural improvement found with HWA-138. The present data provide further evidence of the potential of methylxanthines in the glycerol-ARF murine model.     

The association between angiotensin converting enzyme inhibitor or angiotensin receptor blocker use during postischemic acute transplant failure and renal allograft survival

BACKGROUND: Postischemic acute renal transplant failure occurs in approximately one fourth of all dead donor transplantations. Uncertainty exists regarding the putative association between the use of angiotensin converting enzyme inhibitors (ACEIs) or angiotensin II AT1 receptor blockers (ARBs) and kidney transplant graft survival in patients with delayed allograft function. METHODS: We conducted an open cohort study of all 436 patients who experienced an acute renal transplant failure out of all 2,031 subjects who received their first kidney transplant at the Medical University of Vienna between 1990 and 2003. Actual and functional graft survival was compared between users and nonusers of ACEI/ARB using exposure propensity score models and time-dependent Cox regression models. RESULTS: Ten-year actual graft survival averaged 44% in the ACEI/ARB group, but only 32% in patients without ACEI/ARB (P=0.002). The hazard ratio of actual graft failure was 0.58 (95% confidence interval: 0.35-0.80, P=0.002) for ACEI/ARB users compared with nonconsumers. Seventy-one percent of subjects with ACEI/ARB had a functional graft at 10 years versus 64% of ACEI/ARB nonusers (P=0.027). The hazard ratio of functional graft loss was 0.48 (95% confidence interval: 0.24-0.91, P=0.025). CONCLUSIONS: Use of ACEI/ARB in patients experiencing delayed allograft function was associated with longer actual and functional transplant survival.     

Verapamil reverts acute renal functional impairment induced by angiotensin II converting enzyme inhibitors

Angiotensin converting enzyme inhibitors (ACEI) reduce blood pressure (BP) and provide end-organ protection, but may induce renal function deterioration. In these cases, serum creatinine (SCr) can be normalized by ACEI withdrawn. In some patients, it could be desirable to maintain the ACEI for the protection of the kidney and heart. The objective of the study was to evaluate the effect of Verapamil (V) on renal function added to patients with elevated SCr due to ACEI treatment. In 46 hypertensive patients without previous renal failure, in which ACEI treatment induced an acute increase in SCr (> or = 20% or 0.5 mg/dL), ACEI treatment was maintained and 180 mg/day of V was added for 12 weeks. Those patients showing further SCr increase or no BP control at four weeks were withdrawn. Patients under BP control were moved on the combination V 180 + Trandolapril 2 mg/day for eight weeks more. SCr decreased from 136 +/- 49 micromol/L at baseline to 126 +/- 49 at 12 weeks after adding V (p < 0.001) and to 111 +/- 31 micromol/L at 20 weeks (p < 0.01). Creatinine clearance increased from 62 +/- 22 mL/min at baseline to 68 +/- 28 after 12 weeks of V (p < 0.001). This article demonstrates than in patients with acute renal function impairment secondary to ACEI treatment, the addition of 180 mg/day of verapamil to ACEI reverses SCr towards previous values.     

Selective inhibition of thromboxane synthesis in glycerol-induced acute renal failure

It has recently been postulated that thromboxane A2 may participate in the pathogenesis of acute myohemoglobinuric experimental acute renal failure. To investigate this further, the effect of selective inhibition of thromboxane synthesis on the course of glycerol-induced acute renal failure was determined. Despite significant inhibition of thromboxane synthesis by 4-imidazole-yl-acetophenone, the functional and morphologic disturbance induced by glycerol was unaltered. Moreover, pretreatment with 4-imidazole-yl-acetophenone failed to prevent the fall in renal blood flow seen following glycerol administration. These results argue against a major role for thromboxane A2 in the pathogenesis of this form of experimental acute renal failure.     

Effects of prednisolone on angiotensin converting enzyme activity

Plasma angiotensin converting enzyme was measured in 23 asthmatic subjects before and after administration of prednisolone, 20 mg daily, for seven days. Plasma specimens from seven patients with asthma, seven with sarcoidosis and 14 normal subjects were also assayed before and after the addition of prednisolone in vitro. A plasma free extract of normal lung was also prepared and assayed before and after prednisolone treatment. Mean angiotensin converting enzyme activity was significantly greater in the asthmatic patients (40.3 nmol min-1 ml plasma-1) than in the control population (35.1 nmol min-1 ml plasma-1), though remaining within the 95% reference range. A fall in plasma angiotensin converting enzyme levels was seen after the addition of prednisolone in asthmatics both in vivo and in vitro. Similar in vitro falls were seen in patients with sarcoidosis but not in controls or in normal lung extract. No changes in angiotensin converting enzyme activity were seen after a single dose of 20 mg prednisolone in normal volunteers. Patients with asthma therefore appear to have higher mean angiotensin converting enzyme activities than the normal population and these fall after the addition of prednisolone whether this is added in vivo or in vitro.     

Lung angiotensin converting enzyme activity in chronically hypoxic rats.

A study was carried out to test the hypothesis that the reduced lung angiotensin converting enzyme (ACE) activity which occurs in chronic hypoxia is related to the development of pulmonary hypertension rather than to hypoxia per se. Right ventricular mean systolic pressure (Prvs, mm Hg) and ACE activity (nmol/mg protein/min) in lung tissue homogenates were measured in seven groups of four rats placed in a hypobaric chamber (380 mm Hg; 51 kPa) for two to 24 days. Identical measurements were made on 11 groups of four rats, which were placed in the chamber for 24 days and then allowed to recover in room air for one to 153 days. After two days of hypoxia the mean Prvs (25.5 (SD 3.7] and the mean lung ACE activity (56 (4.6] did not differ significantly from control values. Exposure to hypoxia for four to 24 days caused a progressive increase in mean Prvs to 44.4 (5.9) and a progressive reduction in mean lung ACE activity to 34 (4.0). During recovery lung ACE activity increased and Prvs decreased, so that normal values were achieved by 15 and 56 days respectively. Decreased lung ACE activity may be related to haemodynamic factors associated with pulmonary hypertension rather than to hypoxia.     

Effect of vitamin E and pentoxifylline on glycerol-induced acute renal failure

The pathogenesis of acute renal failure may involve, among other causes, ischemia, vascular congestion, arachidonic acid pathways, and reactive oxygen metabolites. The aim of this study is to evaluate the effects of pentoxifylline and vitamin E on the prevention of experimental acute renal failure induced by glycerol. Eighty-five Sprague-Dawley rats weighing 170-230 g were included in the study. The rats were randomly divided into four groups: group 1 was given 1 ml saline; group 2, glycerol; group 3, glycerol plus vitamin E, and group 4, glycerol plus pentoxifylline. Extent of histological renal tubular necrosis and regeneration in each animal were graded. Blood urea nitrogen, serum creatinine, and creatine kinase concentrations were measured. Mean blood urea nitrogen and serum creatinine concentrations and tubular injury scores were significantly lower in group 1 than in groups 2-4 (p < 0.001), but there were no significant differences among groups 2-4. We conclude that postinsult administration of vitamin E and pentoxifylline does not have a beneficial effect on prevention and severity of acute renal failure and that controlled, multicenter studies involving a large number of patients are needed to clarify this subject.     

Somatic angiotensin converting enzyme in varicocele

The ACE is found as two isozymes in the body. A somatic isozyme found in blood and several other tissues, and a testis-specific isozyme found only in developing spermatids and mature sperm. In this study, we investigated the ACE activity in left spermatic vein blood samples of infertile patients with varicocele and its correlation to spermatologic parameters. The somatic ACE activities were determined in the peripheral and left spermatic vein blood samples from 31 infertile patients who underwent variococelectomy, and 11 fertile control subjects underwent left inguinal herniorraphy. The somatic ACE activity was measured by kinetic spectrophotometric assay. Semen analyses were performed according to WHO guidelines. The mean somatic ACE activities of peripheral and left spermatic veins of the varicocele group were 60.3 +/- 23.0 and 60.2 +/- 23.2 U/L, respectively. In control group, peripheral and left spermatic vein ACE activities were found as 56.8 +/- 17.1 and 56.5 +/- 15.5 U/L, respectively. There was no significant difference between the ACE activity in peripheral and left spermatic vein blood sample from the varicocele and control group. There was no statistically significant correlation between the spermatologic parameters and ACE activities in the spermatic and peripheral vein in both of varicocele and control groups. As a result, it may be suggested that the somatic ACE has no causative role in pathophysiology of varicocele and varicocele related infertility.     

Interleukin-6 stimulates tubular regeneration in rats with glycerol-induced acute renal failure

Interleukin-6 stimulates tubular regeneration in rats with glycerol-induced acute renal failure. BACKGROUND: Interleukin 6 (IL-6) is a pleiotropic cytokine released after endotoxemia, trauma and organ injury. IL-6 may act in cellular proliferation activating transduction signals and Ras/Map cascade or the HGF/c-met axis. We tested the effect of IL-6 in the regeneration of tubular epithelia after acute tubular necrosis (ATN) in rats. METHODS: Rats with glycerol-induced acute renal failure (Gly-ARF) were treated with IL-6 200 microg/kg/day. Functional, histological and immunohistochemical tests were done 24 and 72 h after Gly-ARF to localise mitotic cells (BrdU). The renal expression of c-met (Western-Blot) and circulating levels of HGF (ELISA) were also determined. RESULTS: Rats with Gly-ARF had reduced creatinine clearance that was not influenced by IL-6. The histological appearance of ATN was also unaffected by IL-6. The IL-6 treated rats showed a significant increase in tubular cell proliferation in cortex and medulla, as well as in the expression of c-met protein in the renal cortex, compared to untreated Gly-ARF rats. The plasma HGF concentration was equally elevated in treated and untreated Gly-ARF rats. DISCUSSION: IL-6 stimulates tubular regeneration after Gly-ARF and increases the expression of c-met in the renal cortex. Gly-ARF rats have high circulating levels of HGF that is targeted to act in the injured kidneys by the IL-6 overexpressed renal c-met.     

Effects of melatonin administration to rats with glycerol-induced acute renal failure

Melatonin, the pineal hormone with antioxidative properties was administered to rats with glycerol-induced myoglobinuric acute renal failure (Gly-ARF). This model is characterized by acute tubular necrosis mediated by heme-iron oxidative stress. Rats received melatonin (20 mg/kg) concomitant and 3 h after glycerol injection. Gly-ARF rats showed at 24 h a 78% reduction in glomerular filtration rate, whereas this decrement was significantly reduced to 35% in the melatonin treated Gly-ARF rats. Tubular function evaluated by tubular reabsorption of sodium and lithium was also preserved in melatonin treated rats. The histologic analysis revealed extensive cortical tubular necrosis that was significantly reduced by melatonin treatment. The renal concentration of malondialdehyde (MDA) was increased 6 h after glycerol injection in Gly-ARF and this elevation was prevented when melatonin was administered. Renal concentration of reduced glutathione (GSH) was decreased at 6 h in Gly-ARF and melatonin did not reverse this decrease. It was concluded that melatonin administration attenuated the renal injury in the glycerol model of acute renal failure and reduced kidney oxidative stress through a GSH-independent mechanism.     

Lung angiotensin converting enzyme activity in rats with pulmonary hypertension.

We have studied serum and lung tissue angiotensin converting enzyme (ACE) activity in female Wistar rats with pulmonary hypertension induced by two different methods. Chronic pulmonary hypertension was produced in one group of 10 rats (CH) by confinement in a hypobaric chamber (380 mmHg) for three weeks, and in another group fo 10 rats (M) by a single subcutaneous injection of monocrotaline (60 mg/kg body weight). In these two groups of tests rats and in 20 untreated controls (C), we evaluated right ventricular mean systolic blood pressure (Prvs mmHg), right ventricular hypertrophy, and serum ACE (n mol/ml/min). In lung tissue homogenate, we measured the specific activity of ACE (n mol/mg protein/min), alkaline phosphatase (AP) (IU/mg protein) and lactic dehydrogenase (LDH) (IU/mg protein). The Prvs in groups, C, CH, and M was 25 +/- 7 SD, 41 +/- 7, and 51 +/- 5, respectively. The ratio of right ot left ventricular weight (RV/(LV + S)%) in groups, C, CH, and M was 29 +/- 4, 52 +/- 5, and 56 +/- 7, respectively. The lung tissue ACE in groups C, CH, and M was 85 +/- 11, 65 +/- 20, and 22 +/- 5, respectively. In groups CH, and M the Prvs and RV/(LV + S)% were significantly elevated above control values while lung ACE was significant decreased (p less than 0.05). There was a significant inverse relationship between lung ACE on one hand, and Prvs (r = - 0.73) and RV/(LV + S)% (r = - 0.71) on the other hand. Serum ACE and lung AP were unchanged. In group M there was a slight but significant reduction in lung LDH. Chronic pulmonary hypertension, irrespective of its method of production, is associated with decreased lung ACE. The reduction in lung ACE is inversely proportional to the severity of pulmonary hypertension and right ventricular hypertrophy.     

Reduction of albuminuria after angiotensin converting enzyme inhibition in various renal disorders

The urinary albumin excretion measured by the albumin creatinine clearance ratio (Calb/Ccreat) and the mean supine arterial blood pressure (MAP) were studied before the start of ACE inhibition, at the start and during up to 1 year of ACE inhibition with Captopril or Enalapril in 35 patients with various chronic proteinuric renal disorders with or without renal failure, arterial hypertension and nephrotic syndrome. Before the start of ACE inhibition mean Calb/Ccreat, MAP, s-albumin and s-creatinine did not change. During ACE inhibition the Calb/Ccreat was reduced from 75% (p less than 0.05) in patients with minimal albuminuria to 41% (p less than 0.005) in patients with extensive albuminuria. Average reduction of albuminuria was 44% at one year's observation time. Serum albumin increased 9% (p less than 0.05), serum creatinine did not change significantly and MAP showed a slight, not uniformly significant decrease. The reduction of Calb/Ccreat was of the same order in the different renal disorders studied and was independent of the renal function, presence or absence of nephrotic syndrome and treatment with antihypertensive or immunosuppressive drugs. The decrease in Calb/Ccreat during ACE inhibition was related to the reduction in MAP at most time intervals, but Calb/Ccreat decreased also when MAP was unchanged or increased. Thus the decrease in Calb/Ccreat during ACE inhibition does not only seem to be a consequence of a decrease in the systemic arterial blood pressure but reasonably also due to changes in the intra-renal hemodynamics and most probably a decrease in the glomerular capillary pressure.     

骨化三醇对糖尿病大鼠肾脏血管紧张素转换酶与血管紧张素转换酶2的影响

目的观察血管紧张素转换酶（angiotensinconvertingenzyme,ACE）和血管紧张素转换酶2（angiotensinconvertingenzyme2,ACE2）在糖尿病大鼠肾脏的表达及骨化三醇对其的影响。方法6～8周龄Wistar大鼠被随机分为3组,分别为对照组、糖尿病组、骨化三醇组（O．03μg·kg-1·d-1）。16周后处死各组大鼠,留取标本。放射免疫法检测尿胆微球蛋白（p2-microglobulin,p2-MG）、尿白蛋白（urinaryalbumin,Alb）、血全段甲状旁腺素（intactparathyrin,iPTH）;分光光度法检测尿肌酐（urinecreatinine,UCr）;苦味酸法检测血肌酐（serumcreatinine,SCr）;全自动生化仪检测血钙（Ca）和血磷（P）。PAS染色观察肾脏病理改变并进行半定量统计学分析。实时定量基因扩增荧光（quan—titativepolymerasechainreaction,QPCR）检测肾脏中ACE和ACE2mRNA表达。免疫组织化学法检测肾脏中ACE和ACE2蛋白表达。结果与糖尿病组相比,骨化三醇组尿陀一MG、尿Alb／UCr降低（P〈0．05）,内生肌酐清除率（endogenouscreatinineclearancerate,CCr）升高（P〈O．05）。各组大鼠血Ca、血P及iPTH差异无统计学意义（P〉0．05）。PAS病理染色及半定量分析结果提示,与糖尿病组相比,骨化三醇组大鼠肾脏肾小球硬化程度及肾小管间质纤维化程度有所减轻（P〈0．05）。与对照组比较,糖尿病组大鼠肾脏ACE与ACE2mRNA和蛋白表达均升高（P〈O．05）,ACE／ACE2升高（P〈0．05）。与糖尿病组比较,骨化三醇组大鼠肾脏ACEmRNA和蛋白的表达降低（P〈O．05）,ACE2mRNA和蛋白的表达升高（P〈（）．05）,ACE／ACE2降低（P〈0．05）。相关分析结果显示,尿82-MG、Alb／ucr与ACE／AcE2呈正相关（P〈0．05）,CCr与ACE／ACE2呈负相关（P〈0．05）。结论骨化三醇降低糖尿病大鼠蛋白尿、升高CCr,改善病理损伤,其肾脏保护作用可能与调节ACE和ACE2的表达有关。     

Effect of N-acetylcysteine on antioxidant status in glycerol-induced acute renal failure in rats

Myoglobinuric acute renal failure has three pathogenic mechanisms: tubular obstruction, renal vasoconstriction, and oxidative stress. The latter is generated through the iron released from the group hemo of the myoglobin. Iron induces the formation of high-activity oxygen free radicals that increase oxidative stress and provoke lipid peroxidation and cellular death. This oxidative stress can be measured in several ways, both total or partially with the total antioxidant status or the intermediate enzymes. On the other hand, N-acetylcysteine is a demonstrated substance with antioxidant properties. The aim of the present work was to assess the effect of N-acetylcysteine on the oxidative stress in the glycerol-induced acute renal failure in rats model. We observed that the animals treated with N-acetylcysteine showed an improvement in the antioxidant activity given by an increase in the total antioxidant status and glutathione reductase levels in serum. This improvement was greater when treatment was administered before the induction of rhabdomyolysis. Nevertheless, the observed increase in antioxidant status was only statistically significant for glutathione reductase but not for total antioxidant status. Our results support an important role for N-acetylcysteine in the treatment of this form of acute renal failure, although we think that oxidative stress is not the main pathogenic mechanism of the tubular necrosis induced by rhabdomyolysis, tubular obstruction and renal vasoconstriction being still more important.     

Pre- or post-treatment with hepatocyte growth factor prevents glycerol-induced acute renal failure

Hepatocyte growth factor (HGF) is known to have beneficial effects against damage in various organs, including liver, kidney and lung, in disease models. Previously, we reported that repeated administration of HGF ameliorates renal dysfunction and histological alteration of glycerol-injected rats, an animal model for severe acute renal failure (ARF). In the present study, we investigated in more detail the efficacy of pre- and post-treatment of HGF in this model. ARF was induced by intramuscular injection of glycerol into the hind limbs of male Wistar rats. The efficacy of pre-treatment was studied by intravenous injection of HGF (1 mg/kg) or vehicle 1 and 18 hours prior to glycerol injection. Pre-treatment of HGF dramatically protected glycerol-induced ARF rats against death, and prevented deterioration of biochemical parameters for renal function. We also analyzed expression of heme oxygenase-1 (HO-1), a cytoprotective protein, in kidney of HGF-injected rats. Intravenous administration of HGF enhanced renal expression of HO-1 mRNA from 1 to 3 hours after injection. Next, as a post-treatment study, HGF (1 mg/kg/3 hours) with dopamine was infused into glycerol-induced ARF rats 7 hours after glycerol injection. Intravenous infusion of HGF after ARF onset also ameliorated renal biochemical parameters. These results indicate that pre-treatment of HGF can improve ARF, and induction of HO-1 expression in kidney may be a cause of the protective effect. In addition, post-treatment of HGF with dopamine was also effective against the establishment of ARF.     

Acute cholestatic liver disease protects against glycerol-induced acute renal failure in the rat

BACKGROUND: It is widely held that liver disease predisposes toward acute tubular necrosis. The present study examines the effect of acute cholestatic liver disease on the susceptibility to glycerol-induced acute tubular necrosis in the rat. METHODS: Acute cholestatic liver disease was induced by ligation of the common bile duct, while the intramuscular injection of hypertonic glycerol was used to induce acute tubular necrosis. Renal injury was assessed by plasma creatinine concentration and renal histology. An in vitro model of heme protein-induced renal injury (hemoglobin in conjunction with glutathione depletion) was employed to assess the cytoprotective effects of bilirubin. RESULTS: Ligation of the common bile duct markedly reduced acute renal injury that occurs in the glycerol model (7.5 mL/kg body weight), as evidenced by a lower plasma creatinine concentration and less severe renal histologic injury. At a higher dose of glycerol (10 mL/kg body weight), ligation of the common bile duct again reduced renal injury and cumulative mortality that occurs five days after the induction of this model of acute renal failure. These protective effects of ligation of the common bile duct could not be ascribed to less severe muscle injury or red cell damage. Ligation of the common bile duct induced heme oxygenase-1 in the kidney and markedly so in the liver. Inhibition of heme oxygenase significantly attenuated, but did not prevent, the protective effects conferred by ligation of the common bile duct. Bilirubin, in low micromolar concentrations, was cytoprotective against heme protein-induced cell injury in vitro. CONCLUSIONS: Ligation of the common bile duct confers resistance to glycerol-induced acute tubular necrosis in the rat, actions that arise, in part, from the induction of heme oxygenase-1 in the kidney and liver. Bilirubin, in micromolar concentrations, protects against heme protein-induced renal injury. Our studies uncover a novel form of acquired resistance to renal injury, occurring, unexpectedly, in the setting of acute cholestatic liver disease. We speculate that such potentially cytoprotective alterations may safeguard the kidney against irreversible functional and structural injury in the hepatorenal syndrome.