The flux of arginine after ischemia-reperfusion in the rat kidney

BACKGROUND: Renal arginine synthesis is regulated by arginine plasma levels. The amino acid arginine is synthesized in the proximal tubule of the kidney. Renal ischemia reperfusion (I-R) injury as seen after shock, trauma and major vascular surgery, leading to acute tubular necrosis, might reduce arginine production. METHODS: Wistar rats received either bovine liver arginase (ASE), to lower arginine plasma levels, or saline (SAL). Following the ASE or SAL infusion, rats were randomized to receive a renal artery clamp for 70 minutes, followed by 150 minutes of reperfusion. Renal arteriovenous blood samples were measured and plasma flow was calculated in the I-R kidney (SAL/I-R and ASE/I-R) and the contralateral kidney (SAL/C-L and ASE/C-L) in order to determine renal arginine metabolism. RESULTS: Arginase infusion resulted in lower arginine plasma levels compared to SAL treatment (SAL/I-R vs. ASE/I-R, P < 0.005, and SAL/C-L vs. ASE/C-L, P < 0.005). Renal plasma flow was similar for all groups. The kidney switched from arginine production into arginine uptake after ischemia reperfusion (SAL/I-R vs. SAL/C-L, P < 0.01, and ASE/I-R vs. ASE/C-L, P < 0.01). Renal uptake of glutamine and citrulline increased after ischemia reperfusion (SAL/I-R vs. SAL/C-L and ASE/I-R vs. ASE/C-L, both P < 0.01). Histopathological slices of the kidney showed significantly higher counts of hyperchromasia, pyknosis, nuclear fragmentation and mitoses in individual kidney cells after ischemia reperfusion. CONCLUSION: Decreased renal arginine production is observed with unilateral ischemia-reperfusion, and this change in arginine flux could contribute to or slow the recovery from the low plasma levels of arginine seen in conditions like trauma, shock, or after vascular procedures.     

Mesna: a novel renoprotective antioxidant in ischaemic acute renal failure.

BACKGROUND: Reactive oxygen species (ROS) play a key role in renal ischaemia-reperfusion injury. After establishing the in vitro anti-oxidative potential of mesna, a sulfhydryl-containing compound, its effect on kidney function and morphology in a rat model of ischaemic acute renal failure (ARF) was examined. METHODS: Mesna (180 mg/kg) was administered at different time points relative to ischaemia and/or reperfusion onset. Kidney function was assessed by glomerular filtration rate (GFR) and fractional sodium excretion (FE(Na)) before a 45-min period of unilateral renal artery clamping and following 90 min of reperfusion. Mesna was administered by bolus, 30 min before the induction of ischaemia, 5 min before ischaemia, 5 min before reperfusion, and 5 min after the onset of reperfusion. RESULTS: Mesna improved function of the ischaemic kidney at each administration. When mesna was administered 5 min before the onset of reperfusion, GFR reached 90-100% of its pre ischaemic value and FE(Na) was improved by 75%. The beneficial effect of mesna was also demonstrated by light and electron microscopy. Kidneys treated with mesna 5 min before reperfusion resembled ischaemic non-reperfused kidneys and showed subtle morphological and ultrastructural changes compared with ischaemic-reperfused kidneys. Mesna had no haemodynamic effect on renal blood flow and did not induce any osmotic diuresis. CONCLUSIONS: We suggest that mesna acts as an antioxidant. Its antioxidant potential together with optimal protection achieved when administered 5 min before reperfusion, supports the conclusion that mesna scavenges ROS generated at the onset of reperfusion, thus diminishing reperfusion injury and organ damage.     

Prevention of cold ischaemia-reperfusion injury by an endothelin receptor antagonist in experimental renal transplantation.

BACKGROUND: Endothelin (ET) is known to play a role in the pathogenesis of warm ischaemic renal damage, however, little is known about its involvement in renal cold ischaemia. This study was designed to investigate the response of ET after kidney cold ischaemia, and to assess the potential protective effect of bosentan, a dual, non-selective ET(A)/ET(B) receptor antagonist, against cold ischaemia reperfusion injury in a rat model of syngeneic renal transplantation. METHODS: Kidneys from Lewis rats were transplanted, either immediately or after 5 h of cold preservation. After 48 h, contralateral nephrectomy was performed. Rats were organized into three groups: Tr-NoISC, no cold ischaemia; Tr-ISC, 5 h cold ischaemia; and Tr-BOS, 5 h cold ischaemia plus bosentan (100 mg/kg/day, from the day before transplantation until the seventh day post-transplantation). On day 7, plasma and tissue immunoreactive ET (irET), as well as ET mRNA tissue expression, were evaluated. Renal function was measured by means of serum creatinine on days 3, 4, 5 and 7, and by creatinine clearance on day 7. Conventional histology was performed. RESULTS: The ischaemic group had significantly higher plasma irET levels than the non-ischaemic group and significantly lower levels than the bosentan group. Tissue irET levels and ET mRNA expression were similar in the ischaemic and bosentan groups and were higher than in the non-ischaemic group. Throughout the follow-up, serum creatinine was significantly higher in the ischaemic group than in the bosentan group. Moreover, creatinine decreased rapidly in the bosentan group after nephrectomy, whereas it continued to increase for 48 h in the ischaemic group. Kidneys from the ischaemic group showed a higher degree of tubular-cell necrosis and epithelial-cell detachment than kidneys from the bosentan group. CONCLUSIONS: We conclude that cold ischaemia and preservation damage induces an increase in renal ET mRNA and irET expression in the reperfusion phase, contributing both to the deterioration of renal function and to tubular necrosis. Bosentan is effective in protecting kidneys from this cold ischaemia reperfusion damage. Non-selective ET(A)/ET(B) receptor antagonists might be potentially useful in clinical renal transplantation.     

Role of PI3-kinase/Akt signalling pathway in renal function and cell proliferation after renal ischaemia/reperfusion injury in mice

BACKGROUND: PI3K/Akt pathway has been shown to play a critical role in the regulation of mitogenic signalling, apoptosis, cell proliferation and survival in a variety of cells and tissues. The aim of the present study was to investigate the role of PI3K/Akt pathway in the renal ischaemia/reperfusion. METHODS: Four experimental groups, sham-operative mice, vehicle-delivered and wortmannin-treated ischaemic/reperfusion injury mice, wortmannin-treated normal mice were designed to examined serum blood urea nitrogen level, renal injury, proliferating cell nuclear antigen protein and Akt phosphorylation status at 30 min, 90 min, 24 h, 48 h of reperfusion after ischaemic treatment. Wortmannin or its vehicle was given intraperitoneally at 4 h before surgery. Blood urea nitrogen was measured, and immunohistochemistry and western blotting were used to detect the components of PI3K/Akt pathway in the ischaemic/reperfusion injury kidney. RESULTS: PI3-kinase inhibitor wortmannin imposes a deleterious effect on serum blood urea nitrogen level, renal function after renal ischaemia/reperfusion injury in mice. The renal cell proliferation increased after ischaemia/reperfusion injury in mouse, which could be inhibited by wortmannin. Phosphorylation of Akt was increased after ischaemia/reperfusion in the mouse kidney, and reduced by wortmannin administration. CONCLUSION: This primary study suggests that PI3-kinase/Akt signalling pathway play an important role in the regulation of the renal repair after ischaemia/reperfusion injury.     

Effects of fluid and dobutamine treatment on renal function during partial superior mesenteric artery occlusion and reperfusion

OBJECTIVE: We compared the effects of dobutamine, fluid resuscitation and their combination on renal function during experimental intestinal ischaemia and reperfusion. MATERIALS AND METHODS: Superior mesenteric artery (SMA) blood flow was reduced to 30% from the baseline for 120 minutes in 24 anaesthetized pigs (ischaemic group); 24 pigs (sham group) served as non-ischaemic controls. The animals were further assigned into four treatment arms. In the control arms, the animals were given only basic fluid therapy. In the fluid therapy arms, pulmonary capillary wedge pressure (PCWP) was maintained at 10 mmHg with intravenous fluids. In the dobutamine treatment arm, dobutamine hydrochloride was infused at a dose of 10 microg/min/kg. In the combined dobutamine-fluid therapy arms, dobutamine at 10 microg/min/kg was given and PCWP was maintained at 10 mmHg with fluids. At 120 minutes, the occluder was released in all study groups and the animals were followed for an additional 60 minutes. Renal function was evaluated by means of serum and urine creatinine. urine volume and creatinine clearance. Systemic and regional haemodynamics as well as intramucosal pH, intramucosal-arterial pCO2 gradient, and portal venous-arterial lactate gradient were measured. RESULTS: In the ischaemic groups, diuresis increased and serum and urine creatinine decreased significantly in fluid (p < 0.01, p < 0.01 and p < 0.05, respectively) and dobutamine-fluid (p < 0.01, p < 0.001 and p < 0.001, respectively) treated groups during SMA ischaemia. After SMA reperfusion, diuresis decreased in control group (p < 0.05) and in animals treated with dobutamine alone (p < 0.01). In addition, urine creatinine increased in dobutamine treated group (p < 0.05), and creatinine clearance decreased in control group (p < 0.01). Renal function and diuresis during the SMA occlusion and reperfusion did not differ between ischaemic and sham groups. All fluid treated groups had lower serum creatinine during SMA occlusion than control groups (p < 0.001). CONCLUSIONS: Intestinal ischaemia caused by partial SMA occlusion did not influence renal function. On the contrary, SMA reperfusion resulted in a significant impairment of renal function both in ischaemic and sham operated animals. The impairment was most obvious in control groups and in animals treated with dobutamine alone.     

Postischaemic renal cortical microcirculation and tissue oxygenation in the pig

Porcine and human renal physiology are similar in important aspects. Renal cortical microcirculation and its relation to inulin clearance (CIn) was therefore studied before and after renal ischaemia in 28 pigs under continuous intravenous chlormethiazole-pancuronium anaesthesia. The anaesthesia used provided essential stability in central haemodynamics. The animals were studied for 90 min of reperfusion following 0, 30 or 60 min of renal ischaemia. Twelve of the animals (four were subjected to each duration of ischemia) were also studied 18 h after start of reperfusion. Regional blood flow in the superficial renal cortex was measured by laser Doppler flowmetry (LDF), and tissue oxygenation (PtO2) by surface microelectrode technique. These techniques allow continuous or repeated measurements. During the first 90 min of reperfusion, superficial renal cortical blood flow measured by LDF (Qsrc) underwent considerable temporal variation which followed a certain pattern. Thus, when the renal arterial blood flow was restored after ischaemia, we observed an instant peak in Qsrc followed by a decreasing flow until a minimum value (Qmin) was reached between 3 and 9 min after start of reperfusion (tQmin). Thereafter, Qsrc increased until a maximal value (Qmax) was reached between 11 and 64 min after start of reperfusion (tQmax). The parameters tQmin and tQmax were related to inulin clearance 18 h after start of reperfusion (P less than 0.05 and P less than 0.01, respectively). Thus, it might be possible soon after start of reperfusion--to evaluate the severity of ischaemic damage. This could be useful in the evaluation of different prophylactic strategies, since the full extent of the ischaemic damage, as assessed by clearance determinations, cannot be established until hours later.(ABSTRACT TRUNCATED AT 250 WORDS)     

Short-term arterial blood reperfusion of normothermic kidney in renal artery and abdominal aorta reconstructive surgery.

OBJECTIVE: to prevent kidney injury in renal artery and juxta-renal aortic surgery. After 30 min of cross-clamping ischaemia, renal arterial inflow is temporary re-established for 3 min. The aim of the study was to retrospectively analyse the results of this original technique. METHODS: between January 1987 and May 1999, 48 patients underwent kidney short-term arterial blood reperfusion, directly or through the Pruitt-Inahara shunt. The reperfusion was repeated every 30 min of ischaemia, whenever necessary. Fifty control patients underwent <30 min of kidney ischaemia. Patients were assessed by serum creatinine, digital angiography and radioisotope renography using technecium(99). RESULTS: in the study group one patient developed an acute renal failure and died (2% (-95% CI: 0-11%)). In both study and control groups patients showed a similar and moderate but temporary decline in renal function, which returned to preoperative levels after 1 week. CONCLUSIONS: the results of this study indicate that kidney short-term reperfusion may protect renal tissue from prolonged cross-clamping ischaemia (up to 100 min), also in patients considered at high risk for acute renal failure.     

Effects of diltiazem on postischaemic renal cortical microcirculation in the pig

Diltiazem--a calcium entry blocker--was tested in a porcine model under continuous chlormethiazole-pancuronium anaesthesia as protection against renal failure following 60 min of renal ischaemia. Fourteen pigs were randomly allocated to one experimental (diltiazem and ischaemia) and one control group (only ischaemia) (n = 7 in each). Diltiazem was administered as a continuous intravenous infusion started before the ischaemic insult. In two additional animals diltiazem was given but ischemia was not induced. The postischaemic renal cortical microcirculation was simultaneously investigated in four different regions in the left kidney during the first 4 h of reperfusion. Laser Doppler flowmetry (LDF) was performed in two different regions and measurement of tissue oxygenation was done in two other regions. In the two animals treated with diltiazem without ischaemia, only minor variations in central haemodynamic and renal microcirculatory parameters were evident. In the control group (ischaemia), superficial renal cortical blood flow (Qsrc) decreased from 49 +/- 11 (s.d.) arbitrary units at baseline to 24 +/- 4 arb. units 4 h after start of reperfusion (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibody-induced modulation of the leukocyte CD11b integrin prevents mild but not major renal ischaemic injury.

BACKGROUND: CD11/CD18 beta(2) integrins are involved in leukocyte adhesion to the activated endothelium, and therefore represent a possible therapeutic target in the prevention of ischaemic acute renal failure (ARF). METHODS: To assess the effect of an anti-CD11b monoclonal antibody (mAb) in ischaemic ARF, uninephrectomized Fischer rats were subjected to 45 or 60 min of warm renal ischaemia, then received 1 mg of anti-CD11b mAb 5 min before reperfusion. RESULTS: After 45 min of ischaemia, renal function tests at 24 and 48 h were less altered in mAb-treated than in control rats, but after 60 min of ischaemia the same level of renal insufficiency was observed in the two groups. In parallel, milder tubular necrosis and less leukocyte infiltration were observed in the treated group after 45 min of ischaemia, but no difference was seen after 60 min compared to the control group. The mAb was detected on blood neutrophils up to 48 h after infusion and a marked down-regulation of CD11b expression on neutrophil surfaces was documented by flow cytometry. CONCLUSION: These results indicate that anti-CD11b mAb administered prior to reperfusion decreases moderate ischaemic ARF but fails to prevent renal injury secondary to prolonged ischaemia in this model.     

The triphasic pattern of skeletal muscle blood flow in reperfusion injury: an experimental model with implications for surgery on the acutely ischaemic lower limb

A new model of acute lower limb ischaemia has been developed in the rat hind limb. The model has been used to examine the influence on skeletal muscle blood flow of increasing periods of ischaemia and reperfusion. Following restoration of blood flow after 2-6h ischaemia initial gastrocnemius muscle blood flow was reduced. The severity of initial low reflow, indicated by mean perfusion ratios at 0 and 10 min, correlated with the duration of preceding ischaemia (r = 0.83, p less than 0.05) and was greatest in limbs subjected to 6h ischaemia (p less than 0.01 vs. controls at 0, 10 and 60 min after revascularisation). After 60-240 min, reperfusion muscle blood flow returned to normal in limbs subjected to 3, 4 or 5 h ischaemia. In contrast, peak muscle blood flow in limbs that had been ischaemic for 6 h occurred after 120 min, although perfusion remained less than that measured in control limbs (p less than 0.05:6 h ischaemia, 120 min vs. control)-(relative reperfusion). Limbs reperfused after 6 h ischaemia demonstrated a subsequent decline in muscle blood flow between 120 min and 240 min following revascularisation (p less than 0.05). In addition, muscle blood flow at 240 min was no different to that in a totally ischaemic limb (p less than 0.01 vs. controls; ns vs. ischaemic limb) thus representing reperfusion injury.     

Determination of the Optimum temperature for regional renal hypothermia during temporary renal ischaemia.

To determine the optimum temperature at which the in situ kidney should be maintained while it is ischaemic, 47 mongrel dogs were studied. 35 of these underwent 90 minutes of left renal ischaemia with the kidney temperature maintained at 37 degree, 30 degree, 22 degree, 15 degree and 0 degree C respectively. The effect on renal function was determined by measurements of G.F.R. before and at regular 15-minute intervals after the inschaemic period. Computer statistical analysis exposed the optimum temperature to be 15 degree C. Renal artery blood flow, renal histology, 15-Cr labelled platelets and renal arteriography were used to determine the mechanism of ischaemic injury. Quantitation of renal cell injury confirmed that no additional protection to ischaemia could be gained by colling below 15 degree C. 15 degree C is recommended as the optimum temperature for use in clinical renal hypothermia.     

Failure of verapamil to protect from ischaemic renal damage

To reassess the reported protective effects of verapamil in renal ischaemia, we perfused the left kidney of uninephrectomized female Wistar rats with verapamil (0.1 and 1.0 mg/kg) immediately prior to clamping the renal artery for 60 min. When compared to controls, both doses of verapamil failed to afford protection with respect to urine flow, plasma creatinine, creatinine clearance or histology 24 and 48 h after ischaemia, whereas the purine nucleotide inosine (200 mg/kg) was partially protective: mean plasma creatinine 48 h after ischaemia (+/- SEM) was 547 +/- 54 mumol/l in controls, 686 +/- 38 mumol/l with 0.1 mg/kg verapamil, 491 +/- 68 mumol/l with 1.0 mg/kg verapamil and 374 +/- 45 mumol/l with inosine (p less than 0.05 vs. controls). Using the same model, the effect of verapamil 1.0 mg/kg on renal blood flow, creatinine clearance, urine flow and arterial pressure was studied in the first 2 h after ischaemia. Although significant amounts of verapamil were present in the kidney during ischaemia as evidenced by decreases in systemic blood pressure and in renal vascular resistance after unclamping the renal artery, the early course of renal failure was not altered when compared to controls. In conclusion, we have been unable to confirm earlier reports of a protective effect of verapamil in this rat model of ischaemic renal failure. If there is such an effect, its demonstration appears to depend on very specific experimental circumstances. Based on the results of this and other studies, verapamil is unlikely to afford an impressive overall benefit in the clinical setting of ischaemic renal failure.     

Improved GFR and renal plasma perfusion following remote ischaemic conditioning in a porcine kidney transplantation model

Delayed graft function (DGF) complicates approximately 25% of kidney allografts donated after brain death (DBD). Remote ischaemic conditioning (rIC) involves brief, repetitive, ischaemia in a distant tissue in connection with ischaemia/reperfusion in the target organ. rIC has been shown to induce systemic protection against ischaemic injuries. Using a porcine kidney transplantation model with donor (63 kg) recipient (15 kg) size mismatch, we investigated the effects of recipient rIC on early renal plasma perfusion and GFR. Brain death was induced in donor pigs (n = 8) and kidneys were removed and kept in cold storage until transplantation. Nephrectomized recipient pigs were randomized to rIC (n = 8) or non‐rIC (n = 8) with one kidney from the same donor in each group. rIC consisted of 4 × 5 min clamping of the abdominal aorta. GFR was significantly higher in the rIC group compared with non‐rIC (7.2 ml/min vs. 3.4 ml/min; ΔGFR = 3.7 ml/min, 95%‐CI: 0.3–7.2 ml/min, P = 0.038). Renal plasma perfusion in both cortex and medulla measured by dynamic contrast‐enhanced magnetic resonance imaging (MRI) was significantly higher over time in the rIC group compared with non‐rIC. This experimental study demonstrated a positive effect of rIC on early graft perfusion and function in a large animal transplantation model.     

Klotho reduces apoptosis in experimental ischaemic acute renal failure.

BACKGROUND: Klotho is associated with the suppression of several ageing phenotypes. Because high klotho gene expression was detected in the kidney and several studies have found altered expression in animal models, we explored the physiological relevance of klotho expression in the kidney under renal ischemia reperfusion injury (IRI). METHODS: Male Wistar rats were subjected to bilateral renal ischemia or sham operation, followed by reperfusion for 6, 12 or 24 h, or 2 to 10 days. Renal expression of klotho was assessed by real-time PCR or Western blotting. Creatinine levels were determined. Immunohistochemical studies and TUNEL staining were performed. An adenovirus harbouring the mouse klotho gene (ad-kl) was intravenously administered to one group of rats before renal IRI. RESULTS: Renal klotho mRNA and protein expressions were significantly reduced in IRI rats the first day after ischemia. Pre-treatment with ad-kl resulted in a robust induction of klotho mRNA and protein in the liver but not in the kidney. Ad-kl gene transfer improved serum creatinine and the histological changes. Apoptosis induced by IRI was attenuated following ad-kl administration. CONCLUSION: The data suggest klotho to be involved in the pathophysiology of IRI. Downregulation of renal klotho exacerbates ischaemic acute renal failure, and klotho gene induction has therapeutic potential in managing ischaemic renal damage.     

Intrarenal administration of recombinant human soluble thrombomodulin ameliorates ischaemic acute renal failure.

BACKGROUND: Thrombomodulin (TM) is an endothelial anti-coagulant cofactor which also has anti-inflammatory properties. The present study was performed to investigate the effects of recombinant human soluble TM (RHS-TM) on ischaemia/reperfusion (I/R) renal injury. METHODS: A right nephrectomy was performed in rats, and the left kidney was filled with RHS-TM (0.25 mg/kg), argatroban (20 mg/kg) or a vehicle for 45 min. Before reperfusion, the fluid trapped in the kidney was completely removed. At 24 h after I/R, renal cortical blood flow was measured using a CCD video camera, and the kidneys were harvested for the study. Next, cultured human umbilical vein endothelial cells were treated with RHS-TM (2, 10 or 50 mg/ml) or a vehicle, and incubated for 5 h in culture medium containing 300 microM hydrogen peroxide. Apoptotic cell death was analysed by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay. RESULTS: Immunohistochemistry revealed that the level of TM expression decreased in rat kidneys after I/R. RHS-TM significantly decreased blood urea nitrogen and serum creatinine levels. It also prevented a reduction in cortical blood flow, and attenuated tubular damage and macrophage/neutrophil infiltration. In addition, the number of TUNEL-positive cells decreased significantly in rats treated with RHS-TM. In contrast, argatroban, an inhibitor of thrombin did not show significant renoprotective actions. The results of in vitro study showed that RHS-TM significantly suppressed the number of apoptotic cells. CONCLUSION: The transient intrarenal administration of RHS-TM, but not argatroban, to the kidney attenuates I/R renal injury. The present study suggests that RHS-TM would be a useful tool in preventing transplanted kidney damage or treating acute renal failure in the clinical setting.     

Atorvastatin preserves renal function in chronic complete unilateral ureteral obstruction

PURPOSE: The pleiotropic effects of hMG-CoA (3-hydroxy-3-metylglutaryl coenzyme A) reductase inhibitors may provide renal protection in chronic kidney disease. We examined whether atorvastatin administration preserved renal function in rats with chronic unilateral ureteral obstruction. MATERIALS AND METHODS: Renal clearance experiments were performed in sham operated rats and rats subjected to 3 or 12-day unilateral ureteral obstruction. Hemodynamics parameters and urinary microalbumin levels from the obstructed kidney were also measured. The rats were maintained on a regular diet or the same diet but supplemented with atorvastatin (50 mg/kg daily). RESULTS: Atorvastatin administration did not alter plasma total cholesterol but it significantly decreased triglyceride levels. In sham operated and 3-day unilateral ureteral obstruction rats atorvastatin treatment did not have effects on the glomerular filtration rate or effective renal plasma flow and it also did not affect urinary microalbumin levels. In rats with 12-day unilateral ureteral obstruction the glomerular filtration rate but not effective renal plasma flow was significantly higher and urinary microalbumin was significantly lower in atorvastatin treated rats than in those without atorvastatin treatment. CONCLUSIONS: Atorvastatin treatment decreased microalbuminuria and helped preserve filtration function in chronic unilateral ureteral obstruction without altering plasma cholesterol levels, suggesting that pleiotropic renal protection is offered by this statin.     

Localization of renal oxidative stress and inflammatory response after lithotripsy

OBJECTIVE

To determine if the acute renal oxidative stress and inflammation after extracorporeal shock wave lithotripsy (ESWL), thought to be mediated by ischaemia, is most severe in the portion of the kidney within the focal zone of the lithotripter, and if these effects result primarily from ischaemic injury.

MATERIALS AND METHODS

Pigs (7–8‐weeks old) received either 2000 shock waves at 24 kV to the lower‐pole calyx of one kidney or unilateral renal ischaemia for 1 h. A third group (sham) received no treatment. Timed urine and blood samples were taken for analysis of lipid peroxidation and the inflammatory cytokines, tumour necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6). At 4 h after treatment, kidneys were removed and samples of cortex and medulla were frozen for analysis of cytokines and heme oxygenase‐1 (HO‐1).

RESULTS

ESWL did not affect urinary excretion of malondialdehyde, but did elicit an eight‐fold induction of HO‐1 in the portion of the renal medulla within the focal zone of the lithotripter (F2), while remaining unchanged elsewhere in the treated kidney. There was no induction of HO‐1 in renal tissue after ischaemia‐reperfusion. Urinary excretion of TNF‐α increased from the lithotripsy‐treated kidney by 1 h after treatment, but was unaffected by ischaemia‐reperfusion. As with the HO‐1 response after lithotripsy, IL‐6 increased only in the renal medulla at F2. By contrast, ischaemia‐reperfusion increased IL‐6 in all samples from the treated kidney.

CONCLUSION

These findings show that the acute oxidative stress and inflammatory responses to ESWL are localized to the renal medulla at F2. Furthermore, the differing patterns of markers of injury for ESWL and ischaemia‐reperfusion suggest that ischaemia is not the principal cause of the injury response after ESWL.     

Haemodynamic effects of valsartan in acute renal ischaemia/reperfusion injury.

BACKGROUND: Acute deterioration of renal function is an important side-effect of angiotensin-converting enzyme (ACE) inhibitors, especially if accompanied by other nephrotoxic events. Angiotensin II receptor(1) blockers (ARB) are thought to have fewer side-effects on renal perfusion and function. We examined the effects of valsartan (VAL) on kidney function as well as the contribution of the nitric oxide (NO) system in a rat model of ischaemic acute renal failure (ARF). METHODS: ARF was induced by 40 min of clamping of both renal arteries in female Sprague-Dawley rats. Renal haemodynamic and tubular parameters were determined during post-ischaemic infusion of vehicle, VAL, VAL and the NO-synthase substrate L-arginine, and VAL together with inhibition of NO synthases (NOS) by L-NMMA. RESULTS: Clamping induced acute renal failure with marked decreases in glomerular filtration rate (GFR) and renal plasma flow (RPF) accompanied by a rise in renal vascular resistance (RVR) and fractional sodium excretion. Valsartan caused a slight but significant improvement of GFR and RPF without full recovery of renal function and caused a lowering of RVR and tubular sodium loss. L-arginine-co-administration had no additive beneficial effect. Valsartan-induced changes were not significantly depressed by unspecific inhibition of NOS. CONCLUSIONS: Inhibition of the angiotensin II-receptor(1) diminishes the deleterious effects of ischaemia and reperfusion on glomerular function and on the renal microcirculation. An involvement of the NO system could not be demonstrated.     

Attenuation of reperfusion injury by renal ischaemic preconditioning: the role of nitric oxide

OBJECTIVE: To determine the effect on nitric oxide (NO) release and renal NO synthase (endothelial, eNOS and inducible, iNOS) activity of renal ischaemia-reperfusion (I/R) in vivo in an animal model, and to examine the possible involvement of NO in ischaemic preconditioning (IP) of the kidney. MATERIALS AND METHODS: In a right-nephrectomized rat model, 42 animals were randomized in four groups: controls; IP-only (4 min of ischaemia followed by 11 min of reperfusion, total of four cycles); renal warm ischaemia (45 min) and 6 h reperfusion; ischaemia (45 min) preceded by IP pretreatment. Serum NO metabolites were assayed 2 and 6 h after ischaemia or the control equivalent. NOS expression in the kidney was detected immuno-histochemically, and damage assessed morphologically in sections stained with haematoxylin and eosin. Kidney function was assessed by the levels of serum creatinine, urea and electrolytes. RESULTS: Compared with before ischaemia, the concentration of serum NO metabolites at 6 h was increased in the IP-only animals (P = 0. 016) and in the IP + I/R group (P = 0.002). There was greater eNOS expression in the IP-only group (P = 0.009) and in the IP + I/R group than in controls (P = 0.050). iNOS expression was greater in the IP-only animals than in the control group (P = 0.050). Histological assessment showed less evidence of cellular damage in IP + I/R animals than in the I/R-alone group (P = 0.020). Serum creatinine level was not significantly different between the IP-only group and the control. There were no differences after 2 h of reperfusion. CONCLUSION: Ischaemic preconditioning has a protective effect on renal structure and function, which may be produced by increased NO release arising from increased NOS expression by 6 h after reperfusion.     

Protective effect of UR-12670 on chronic nephropathy induced by warm ischaemia in ageing uninephrectomized rats.

BACKGROUND: In young animals, renal ischaemia/reperfusion injury and mass reduction are associated with chronic lesions that mimic those found in chronic rejection. We have shown that the phospholipid platelet-activating factor (PAF) participates in young animals in such chronic nephropathy. Here we examine the long-term effects of the orally active PAF antagonist, UR-12670 in ageing uninephrectomized rats exposed to prolonged warm ischaemia. METHODS: Fifteen- to eighteen-month-old uninephrectomized male Sprague-Dawley rats were allocated into three groups and followed for 16 weeks: UNx, rats without ischaemia; UNxISC, ischaemic kidney (60 min), and UNxISC+UR, ischaemic kidney and UR-12670 from day 0 to the 16th week. Serum creatinine and proteinuria were monitored every 4 weeks. At the end of the study, conventional histology was performed and monocyte-macrophages were identified with the specific monoclonal antibody ED-1. RESULTS: The UNxISC group had severe acute renal failure with a high mortality rate, which was associated with incomplete restoration of renal function. Renal insufficiency in this group was sustained throughout the follow-up. Both UNx and UNxISC groups developed progressive proteinuria from the 12th week. Though UNxISC+UR group showed similar acute renal failure and mortality rate to the ischaemic non-treated group, serum creatinine decreased to levels similar to UNx group, which were maintained until the end of the study. Treatment of ischaemic kidneys with UR-12670 produced a slight decrease in 24-h proteinuria and a reduction in glomerulosclerosis, the mean tubulointerstitial score and number of monocyte-macrophages to values similar to UNx group. CONCLUSIONS: The chronic administration of the PAF antagonist UR-12670 attenuates the long-term effects of ischaemia-reperfusion injury in uninephrectomized ageing rats. The beneficial effect of this agent suggests that PAF contributes to the progression to late renal damage in this model.