Changes in urinary pH and glomerular filtration rate in partially obstructed canine kidney

The creatinine clearance and urinary pH changes were studied in 12 male dogs in whom the ureters were unilaterally obstructed for periods ranging from 2 days to 27 weeks. The obstruction was then released and the recovery was studied. Using the contralateral kidney as control, significant drop in the creatinine clearance was observed to be consistently associated with failure to produce acidic urine. The obstructed kidneys with urinary pH above 7.00 had significant reduction in creatinine clearance when compared with obstructed kidneys with urinary pH 7.00 or less (p less than 0.005). The marked drop in the creatinine clearance and rise in urinary pH was observed to occur in kidneys obstructed for more than 3 weeks. With obstruction for shorter periods, the ability to produce acidic urine is preserved and the recovery potential is good.     

Chemokine expression in the obstructed kidney.

Chemokines are chemotactic cytokines that are important mediators of leukocyte extravasation and chemotaxis. Herein, we provide evidence that after 1 day of unilateral ureteral obstruction (UUO), the mouse obstructed kidney (OBK) expresses MCP-1 (monocyte chemoattractant protein-1), RANTES (Regulated on activation normal T-cell expressed and secreted) and IP-10 (interferon-gamma-induced protein-10). In addition, by day 7, MIP-2 (macrophage inflammatory protein-2) expression is elevated in the obstructed kidneys compared to the contralateral control kidneys (CLK). After 7 days of obstruction, RANTES was the most abundant of the four chemokines detected in the OBK. In situ hybridization results indicate that several cellular compartments contribute to the expression of RANTES in the OBK. However, clearly cortical tubules within the OBK contribute substantially to the elevated expression of RANTES. These data support the contention that the cortical tubular epithelium plays a pivotal role in the inflammation associated with experimental hydronephrosis.     

Effect of furosemide on the obstructed kidney

The effect of furosemide on the obstructed kidney was studied in dogs. In control kidneys (n = 4) the renal blood flow (RBF) was increased transiently after intravenous infusion of 20 mg of furosemide; from 12.9 +/- 1.2 to 14.8 +/- 1.4 ml/min/kg.B.W. No change in the renal pelvic pressure was observed. Urine flow increased from 0.47 +/- 0.12 to 4.98 +/- 1.15 ml/min at 20 minutes after furosemide administration. Increases in the fractional fluid excretion rate (V/GFR), the fractional sodium excretion rate (FENa) and the fractional potassium excretion rate (FEK) were observed and the maximum values were obtained at 20 minutes after furosemide administration. In two-week unilateral incompletely obstructed kidneys (incomplete UUO; n = 5), RBF was lower than that of the control kidney, whereas a tendency of transient increase was also noticed after furosemide administration; from 8.4 +/- 1.9 to 10.5 +/- 2.3 ml/min/kg.B.W. The renal pelvic pressure increased immediately and transiently after furosemide infusion. Increase in the urine flow was significant, but the value was lower than that of control, and the maximum value was marked at 20 minutes after furosemide administration. V/GFR, FENa and FEK were also increased in incomplete UUO, but the peak values were lower than those of control. In two-week unilateral completely obstructed kidneys (complete UUO; n = 5), RBF was markedly decreased (3.14 +/- 0.38 ml/min/kg.B.W.), and no significant increase was noticed after furosemide administration. The renal pelvic pressure was gradually and continuously increased after furosemide infusion. The fractional excretion rate of pelvic urine components was variable. In particular, V/GFR was significantly increased 60 minutes after furosemide administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Didelphic uterus and obstructed hemivagina resulting in obstructed hydronephrosis of transplanted kidney

Uterine didelphys are rare malformations involving the Mullerian ducts. The incidence ranges from 0.1% to 3.8%. This wide range could be because of inaccurate diagnosis or to the fact that many of these diagnoses are not detected during the women's lifetime. Here, we report the management of a 16-year-old female patient who had uterine didelphys with obstructed hemivagina, resulting in obstructive hydronephrosis in her transplanted kidney.     

Nestin expression in the kidney with an obstructed ureter

Nestin is an intermediate filament protein originally identified in neuroepithelial stem cells. This cytoskeletal-associated protein is also expressed in some non-neuronal organs including renal tubular cells and glomerular endothelial cells during kidney development. Little is known, however, about nestin expression in the kidney during injury. In this study, we find nestin expression induced in renal tubular and interstitial myofibroblasts in the adult rat kidney following unilateral ureteral obstruction. The degree of nestin expression was well correlated with the degree of tubulointerstitial fibrosis. Immunohistochemical identification of specific nephron segments showed that nestin was primarily expressed by proximal tubules, partially by distal tubules and thick ascending limbs of Henle but not by collecting ducts. The nestin-positive tubular cells also expressed vimentin and heat-shock protein 47 (HSP47) suggesting these cells reverted to a mesenchymal phenotype. Not all vimentin- or HSP-expressing cells expressed nestin; however, suggesting that nestin is distinct from these conventional mesenchymal markers. Nestin expression was also found associated with phenotypical changes in cultured renal cells induced by hypoxia or transforming growth factor-beta. Nestin expression was located in hypoxic regions of the kidney with an obstructed ureter. Our results indicate that nestin could be a novel marker for tubulointerstitial injury.     

Extracellular signal-regulated kinase-dependent interstitial macrophage proliferation in the obstructed mouse kidney

Aim:   A number of growth factors have been shown to induce proliferation of renal cell types in animal models of kidney disease. In vitro studies suggest that many such growth factors induce renal cell proliferation through the extracellular signal-regulated kinase (ERK) pathway. The aim of this study was to determine the functional role of ERK signalling in cell proliferation in the obstructed kidney.
Methods:   Unilateral ureteric obstruction was induced in C57BL/6J mice which then received an ERK inhibitor drug (U0126 100 mg/kg t.i.d.), vehicle (DMSO) or no treatment, starting at day 2 after unilateral ureteric obstruction surgery and continuing until animals were killed on day 5. Cell proliferation was assessed by uptake of bromodeoxyuridine (BrdU).
Results:   In normal mice, phosphorylation (activation) of ERK (p-ERK) was restricted to collecting ducts. Western blotting identified a marked increase in p-ERK in the obstructed kidney in the no-treatment and vehicle-treated groups. Immunostaining showed strong p-ERK staining in many tubules and in interstitial cells. U0126 treatment inhibited ERK phosphorylation as assessed by western blot and immunostaining. The number of BrdU+ cortical tubular cells was reduced by vehicle treatment but was not further changed by U0126 treatment. In contrast, interstitial cell proliferation in the obstructed kidney was unaltered by vehicle treatment, but this was significantly inhibited by U0126. This was associated with a reduction in interstitial macrophage accumulation, but no effect was seen upon interstitial accumulation of α-SMA+ myofibroblasts. Renal fibrosis, as assessed by collagen deposition, was unaffected by U0126 or vehicle treatment.
Conclusion:   These studies show that accumulation of interstitial macrophages in the obstructed kidney is, in part, dependent upon the ERK signalling pathway.     

Percutaneous catheter drainage of obstructed transplant kidney in pregnancy

Obstruction of a transplanted kidney may occur during pregnancy and necessitate early cesarean section, with considerable risk to the immature fetus. We report a case where percutaneous catheter nephrostomy relieved the obstruction and allowed the pregnancy to progress until the fetus was mature.     

Parathyroid hormone-related protein promotes inflammation in the kidney with an obstructed ureter

Parathyroid hormone-related protein (PTHrP) promotes fibrogenesis in the acutely damaged kidney. Considering the relation between fibrosis and inflammation, we studied transgenic mice that overexpress PTHrP in the proximal tubule. When unilateral ureteric obstruction was induced in these transgenic mice, we found that they had more renal tubulointerstitial damage, leukocyte influx, and expression of proinflammatory factors than their control littermates. Reversal of PTHrP constitutive overexpression in these transgenic mice or treatment of control mice with the PTHrP antagonist (7-34) decreased this inflammatory response. Losartan, which abolished obstruction-induced endogenous PTHrP upregulation, also decreased the latter response but less effectively in transgenic mice. The PTHrP fragment (1-36) induced nuclear factor-kappaB (NF-kappaB) activation and proinflammatory cytokine overexpression in mouse cortical tubule cells in culture as well as migration of the macrophage cell line Raw 264.7. All these effects were decreased by PTHrP (7-34) and NF-kappaB or extracellular signal-regulated kinase (ERK) activation inhibitors. Our findings suggest a critical role of PTHrP in the renal inflammatory process that results from ureteral obstruction and indicate that ERK-mediated NF-kappaB activation seems to be an important mechanism whereby PTHrP triggers renal inflammation.     

Activation of the ERK pathway precedes tubular proliferation in the obstructed rat kidney

BACKGROUND: In vitro studies suggest that activation of the extracellular signal-regulated kinase (ERK) pathway plays a critical role in the proliferation of tubular epithelial and myofibroblast-like cells. However, little is known of ERK activation in individual cell types in normal or diseased kidney. The aims of this study were to (1) localize ERK activation within the kidney, and (2) examine the relationship between ERK activation and cell proliferation in the injured kidney. METHODS: Unilateral ureteric obstruction (UUO) was induced in groups of six Wistar rats, which were killed at 30 minutes, 6 hours, and 1, 4, or 7 days after obstruction. Activation of ERK was identified using antibodies specific for the phosphorylated form of ERK (pERK) in Western blots and immunostaining. Proliferating cells were detected using bromodeoxyuridine (BrdU). RESULTS: Western blotting showed abundant expression of the two ERK isoforms, ERK-1 and ERK-2, in normal rat kidney. Low levels of activated ERK (pERK-2> pERK-1) were detected in normal rat kidney by Western blotting. Immunostaining showed that ERK activation in normal kidney was largely restricted to collecting ducts in the outer medulla. Within 30 minutes of ureter obstruction, Western blotting showed a sixfold increase in ERK activation followed by a second peak (14-fold increase) on days 4 and 7. The initial peak of ERK activation was localized to medullary collecting ducts and the thick ascending limb of Henle (TALH), whereas the second peak corresponded to a progressive increase in ERK activation in dilated collecting ducts and in interstitial cells in the cortex. Proliferation of tubular epithelial cells closely followed the pattern of ERK activation, being evident first in medullary collecting ducts and TALH on day 1, and then in cortical collecting ducts from day 4. CONCLUSION: This study has identified a discrete pattern of ERK activation in normal rat kidney and an increase in ERK activation following obstruction. The temporal and spatial relationship in which ERK activation preceded tubular cell proliferation suggest that ERK signaling plays a key role in tubular epithelial cell proliferation in the injured kidney.     

Enhanced glomerular prostaglandin formation in experimental membranous nephropathy

To determine whether the induction of immune-mediated glomerular injury influences the formation of cyclooxygenase products by glomerular cells, we determined prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) (as the stable metabolite of TXA2) formation in isolated glomeruli of rats with passive Heymann nephritis (PHN). PHN is a model of membranous nephropathy mediated by antibody and complement independent of inflammatory cells. Five days following induction of PHN by injection of heterologous antibody to rat proximal tubular brush border antigen (Fx1A) rats developed proteinuria 36.5 +/- 34 (controls 3.8 +/- 1 mg/day). Treatment with cobra venom factor, which depleted complement C3 levels to less than 10% of baseline, prevented the development of proteinuria (6.9 +/- 2 mg/day). The development of subepithelial, glomerular immune-complex deposits and proteinuria was associated with a significant stimulation of glomerular PGE2 (87%) and TXB2 (183%) formation. This increment in glomerular prostanoid biosynthesis was significantly inhibited (PGE2 increased 22%, TXB2 increased 75%) in animals that were complement depleted with cobra venom factor. Cobra venom factor had no effect on glomerular prostanoid formation in normal rats. In additional experiments we tested the hypothesis that TXA2 may contribute to mediation of proteinuria in PHN. We utilized a thromboxane synthetase inhibitor UK38485. UK38485 reduced glomerular TXB2 formation by 80% without influencing glomerular deposition of 125I-labeled antibody, and did not alter levels of urine protein excretion in rats with PHN (control 42 +/- 21, UK 38485, 39 +/- 24 mg/day, P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term follow-up of separate glomerular filtration rate in partially obstructed kidneys. Experimental study

An often encountered assumption is that non-relieved renal obstruction will lead soon or late to progressive deterioration of the renal function. The effect of non-relieved partial ureteral obstruction on the separate glomerular filtration rate (SGFR) was studied throughout the whole life of a series of rats, who were submitted at the age of 3 months to partial obstruction of the left ureter. An initial and variable postoperative SGFR decrease was gradually observed, but after this period, SGFR remained stable until the natural death of the animal.     

人参皂甙Rg1对梗阻肾的保护作用

目的:探讨人参皂甙Rg1(G- Rg1)对梗阻肾的保护作用。方法:建立大鼠单侧输尿管梗阻(UUO)模型。假手术组:未行输尿管结扎即关腹;非治疗组:行左侧输尿管结扎后关腹;G- Rg1 组:行左侧输尿管结扎后关腹,并给予G -Rg1灌胃[120 mg/(kg·d)]。全部大鼠1 周后处死,取出左肾常规固定。免疫组织化学染色法检测Bax、PCNA、TGF -β1蛋白表达水平,并应用计算机图文系统进行分析。结果:UUO大鼠肾小管上皮细胞、肾间质细胞中Bax、PCNA蛋白表达显著增多,肾间质、肾小球中TGF- β1 蛋白表达显著增多。G- Rg1 明显抑制UUO大鼠肾小管上皮细胞中Bax蛋白表达(P<0.05),促进PCNA蛋白表达(P<0.05);抑制肾间质和肾小球中TGF- β1蛋白表达(P<0.05)。结论:Bax在梗阻肾小管上皮细胞凋亡、TGF- β1 在间质纤维化和肾小球硬化中可能起着重要的作用。G -Rg1可能有抑制梗阻肾小管上皮细胞凋亡、促进上皮细胞增殖、抑制间质纤维化和肾小球硬化的作用。     

C-reactive protein frequently localizes in the kidney in glomerular diseases

AIM: In recent reports, C-reactive protein (CRP) has emerged as a component that may play important roles in atherogenesis. Based on the analogies set out in a previous report between focal-segmental sclerosis and atherosclerosis, we hypothesized that CRP contributes to the pathogenesis of glomerular diseases. To our knowledge, no immunohistochemical study of CRP localization in the kidneys has been previously reported. PATIENTS AND METHODS: In the present study, we investigated 106 kidney biopsy specimens from children with various types of glomerular diseases and minor glomerular abnormalities. Of the 106 cases, 74 were proliferative diseases, 17 were non-proliferative diseases, and 15 were minimal-change nephrotic syndrome (MCNS). Immunohistochemical staining was performed using monoclonal antibody to CRP. RESULTS: CRP immunoreactivity was found in 48 of 106 (45.3%) specimens. CRP deposition was encountered more often in patients with proliferative diseases (56.8%) than in those with non-proliferative diseases (23.5%) (p < 0.01). CRP deposition, most frequently observed along the capillary walls of glomeruli, was found in 33 of 46 (71.7%) cases with positive expression of CRP. CRP was also located in the peritubular capillary walls and small vessels in the interstitium in 13 of 46 cases (28.3%). CRP deposition was also found in 2 of 15 cases of MCNS. The two MCNS specimens showing positive CRP immunoreactivity were both from patients who had undergone cyclosporin therapy. CRP deposition was not shown in any cases treated with steroids or cyclophosphamide. The cases of patients who had undergone renal biopsies within 6 months after onset revealed a tendency toward positive CRP deposition. The clinical outcomes at the latest follow-up were quite similar between the groups of patients with and without CRP deposition. CONCLUSIONS: We surmise that circulating CRP may deposit at the site of endothelial injury, and may not be relevant to the progression of renal lesions.