热休克蛋白70和27在非小细胞肺癌中的表达和临床意义

目的研究热休克蛋白(heatshockprotein,HSP)70和27在非小细胞肺癌(nonsmallcelllungcancer,NSCLC)组织中的表达,探讨HSP70和HSP27与NSCLC细胞的组织学类型、分化和转移之间的关系。方法采用免疫组化SP法检测60例NSCLC标本中HSP70和HSP27的表达情况。结果NSCLC中HSP70和HSP27的表达与肿瘤细胞组织学类型无关。HSP70和HSP27的表达正相关。HSP70的表达与肿瘤细胞分化程度和淋巴结转移明显相关,HSP27的表达则无关。结论HSP70在NSCLC中的高表达与肿瘤细胞的分化和转移明显正相关,提示HSP70可以作为NSCLC辅助诊断和估计预后的指标。而HSP27尽管在多种恶性肿瘤中发挥促进细胞恶变的作用,但在NSCLC中的作用需要进一步研究。     

热休克蛋白70对肾脏缺血预处理保护作用的研究

目的 :研究缺血预处理对肾脏缺血再灌注损伤的保护作用 ,观察热休克蛋白 70 (HSP70 )的表达变化并探讨其作用机制。方法 :建立大鼠肾脏缺血再灌注损伤模型并进行缺血预处理 ,实验分组 :假手术组 (S组 )、缺血再灌注组 (IR组 )和缺血预处理组 (PC组 )。各组再灌注后检测血清肌酐 (Scr)、肾组织丙二醛 (MDA)含量 ,肾组织石蜡切片苏木精伊红染色以及免疫组化染色。结果 :PC组Scr值、肾小管病理评分、肾组织中MDA含量明显低于IR组 (P <0 .0 5 ) ,PC组与S组比较差异无显著性意义 (P >0 .0 5 ) ;HSP70免疫组化染色 :S组未见明显的阳性反应产物 ,PC组和IR组肾小管上皮细胞胞质可见棕黄色阳性反应产物。计算机图像分析显示PC组灰度值显著高于IR组 (P <0 .0 1)。结论 :缺血预处理对肾脏缺血再灌注损伤有明显保护作用 ,其作用机制可能与HSP70本身的细胞保护作用及HSP70的细胞内抗氧化作用有关     

Hypercalciuria in pediatric patients with ureteropelvic junction obstruction is of genetic origin

OBJECTIVE: Genitourinary tract malformations are associated with urolithiasis. Hypercalciuria has been described in children with ureteropelvic junction obstruction (UPJO), although the etiology of this metabolic abnormality remains unknown. This study was conducted to find out whether children with UPJO have a higher prevalence of hypercalciuria and whether their family members are affected by hypercalciuria and/or urolithiasis. MATERIAL AND METHODS: We studied the prevalence of hypercalciuria and urolithiasis in 27 children (14 males, 13 females) with UPJO and their parents. RESULTS: One patient had a history of renal colic, whereas imaging studies showed macroscopic renal lithiasis in two patients and calyceal microlithiasis in four. Hypercalciuria was found in 17/27 children (63%), 15 of whom (88%) had a familial history of urolithiasis: seven families in first-degree relatives, six in second-degree relatives and two in other relatives. Concerning the 10 children without hypercalciuria, seven of them (70%) had a family history of urolithiasis: four in first-degree relatives and three in second-degree relatives. The prevalences of both urolithiasis and hypercalciuria were not influenced by gender. CONCLUSIONS: Urolithiasis is associated with hypercalciuria in patients with UPJO. In accordance with previous data, our results show that the prevalence of hypercalciuria is greater in pediatric patients with UPJO than in the general population. Likewise, the prevalence of urolithiasis in the families of these children is also higher than that in the general population. Hypercalciuria was inherited as an autosomal dominant trait.     

Clusterin production in the obstructed rabbit kidney: correlations with loss of renal function.

Clusterin, a protein associated with cell death, has been suggested as a marker of renal injury. Correlation of clusterin gene expression with changes in renal function and quantitative measurement of clusterin protein levels after ureteral obstruction have not been previously reported. With unilateral ureteral obstruction in rabbits as the experimental model, the time course of alterations in renal function, clusterin mRNA accumulation, and concentrations of clusterin protein in serum, urine, and renal tissue were investigated. RBF, GFR, and renal concentrating ability (percent sodium reabsorption and urine osmolarity) all decreased (P < 0.05) in the obstructed kidney from control values within 1 day of ureteral obstruction. Clusterin mRNA levels started to rise in the ipsilateral kidney within 12 h of ureteral obstruction and increased up to 10-fold above control levels after 3 days of obstruction. Hybridization histochemistry showed that clusterin mRNA was initially detectable in collecting ducts and distal tubules within 12 h of ureteral obstruction. After 7 days of obstruction, increased accumulation of clusterin mRNA was also detectable in proximal tubular epithelial cells. Clusterin gene expression remained elevated in collecting ducts after 60 days of obstruction. Clusterin expression in the contralateral kidney was increased twofold over control values after 12 h of obstruction. No increase in clusterin mRNA accumulation was detectable after 24 h in the contralateral kidney. Total clusterin protein in the obstructed kidney increased from 0.59 +/- 0.66 (mean +/- 1 SD) to 2.5 +/- 1.3 micrograms after 7 days of ureteral obstruction (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Urinary proteome analysis identifies infants but not older children requiring pyeloplasty

One out of every five children suffering from ureteropelvic junction obstruction (UPJO) requires pyeloplasty. This prevalence indicates an urgent necessity to identify high-grade UPJO as early as possible to avoid renal damage. A novel non-invasive proteomic urine test has recently been introduced that is able to detect these patients at an early stage. In the study reported here, we tested this approach to assess its use in our centre and to expand its application to older children. Twenty-seven children (median age 0.4 years, range 0.1–8.8 years) with hydronephrosis who had been scheduled a nuclear diuretic renal scan (DR) to identify urodynamically relevant UPJO were included in our prospective study. Patients with prior surgery of the urinary tract were excluded. The urinary proteome pattern was analysed using capillary electrophoresis coupled to mass spectrometry. Of the 27 children, 11 had a relevant UPJO diagnosed by the DR. In 19 children <1 year of age, urinary proteome analysis predicted obstruction with a sensitivity of 83% (5/6) and a specificity of 92% (12/13). However, in older patients, the sensitivity decreased to 20% (1/5) and specificity to 66% (2/3). Based on our results, the proteome pattern established by Decramer and co-workers predicts the need for surgery in infants but not in older children with UPJO.     

臭氧氧化预处理对大鼠肾缺血再灌注损伤的热休克蛋白表达的影响

目的 探讨臭氧氧化预处理通过诱导热休克蛋白70(HSP70)的合成,保护大鼠肾脏缺血再灌注损伤的作用与机制.方法 建立原位大鼠单侧肾缺血再灌注动物模型,I/R前15 d经直肠吹人氧气和臭氧的混合气体5.0～5.5 ml(臭氧浓度50 mg/L,1 mg/kg体重,每日1次).全自动生化分析仪检测尿素氮(BUN)、肌酐(Cr),比色法测定血清的脂质过氧化产物丙二醛(MDA)、超氧化物歧化酶(SOD).Western blot检测HSP70蛋白的含量;逆转录-聚合酶链反应(RT-PCR)方法检测HSPT0的表达.结果 肾缺血再灌注24 h后,血清中BUN、Cr、MDA明显增高,肾组织内HSP70表达明显增强(P＜0.05),经臭氧氧化预处理后,血清中的BUN、Cr、MDA均降低,SOD升高;HSP70表达升高更加明显(P＜0.05).结论 臭氧氧化预处理可以诱导大鼠肾缺血再灌注组织中HSP70表达,减轻大鼠肾脏缺血再灌注损伤.     

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.     

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.     

Gene expression in response to acute unilateral ureteral obstruction

Acute unilateral ureteral obstruction results in differential growth characteristics of both the ipsilateral and contralateral kidney. The obstructed kidney undergoes cellular atrophy following an initial phase of interstitial proliferation while the contralateral kidney hypertrophies. To evaluate the molecular events occurring in both kidneys after obstruction, we examined the expression of growth related (c-fos, c-myc, cH-ras, HSP 70), cell maintenance (beta-actin), and cellular damage (TRPM-2) genes at the mRNA level. In the contralateral kidney an early and transitory induction of c-fos and c-myc expression occurred while a bimodal induction was noted in the obstructed kidney. The patterns of cH-ras, HSP 70 and actin expression also differed in both kidneys. Induction of TRPM-2 was noted only in the obstructed kidney. Rapid gene activation is evident in both the contralateral and obstructed kidney following unilateral ureteral obstruction. The patterns of expression are distinct and may reflect the cellular response to stress (cell death and stromal proliferation) in the obstructed kidney versus a response to a systemic stimulus resulting in cellular hypertrophy in the contralateral kidney.     

Laparoscopic dismembered pyeloplasty for ureteropelvic junction obstruction in children

Objectives:   To present our initial experience with laparoscopic pyeloplasty and to evaluate the safety and short-term outcome of this technique in children.
Methods:   Thirteen kidney units in twelve children underwent laparoscopic dismembered pyeloplasty for the management of ureteropelvic junction obstruction (UPJO) at our institution between 2005 and 2008. Patient age at surgery was 18–177 months (mean 89.8 months). There were six boys and six girls. Ten had unilateral UPJO with a normal contralateral kidney, one had bilateral UPJO and one had UPJO of a solitary kidney. We used 3- and 5-mm instruments for grasping, blunt dissection, incising and suturing to facilitate safe and precise surgery. The outcome was measured by the operative time and resolution of obstruction and symptoms.
Results:   Median operative time was 275 min (range 154–420). There was a slight relationship between age and operative time. No major perioperative complications occurred in any cases. Median renal pelvic anterior–posterior diameter at ultrasonography significantly decreased from 8.6 cm (range 3.8–22.0) preoperatively to 3.9 cm (1.0–8.9) postoperatively ( P  < 0.05). The median pre- and postoperative split renal function on diuretic renography in unilateral cases was 37.3% (range 29.7–46.4) and 39.5% (27.8–48.0), respectively. Overall, successful resolution of UPJO was observed in 12 of 13 kidneys (92.3%).
Conclusions:   Laparoscopic pyeloplasty represents a safe and effective option in the surgical treatment of children with UPJO.     

Chronic COX-2 inhibition reduces medullary HSP70 expression and induces papillary apoptosis in dehydrated rats

BACKGROUND: Papillary cells adapt to their hyperosmotic environment by accumulating organic osmolytes and by enhanced synthesis of heat shock protein 70 (HSP70), which protect against high-solute concentrations. Because cyclooxygenase-2 (COX-2) is expressed abundantly in the renal papilla and is induced by dehydration, and because HSP70 expression is stimulated by specific prostaglandins, COX-2 inhibition may interfere with cellular osmoadaptation. METHODS: In vivo, rats received rofecoxib before water deprivation. Medullary expression of several tonicity-responsive genes was analyzed and apoptosis was monitored by transferase-mediated dUTP nick-end labeled (TUNEL) staining and determination of papillary caspase-3 activity. In vitro, inner medullary collecting duct 3 (IMCD3) cells were exposed to hypertonic medium containing a COX-2-specific inhibitor. Thereafter, expression of tonicity-responsive genes was analyzed and resistance to high-solute concentrations was examined. Further, the effect of Delta 12-PGJ2, a urinary prostaglandin, and of HSP70 overexpression on resistance against high urea concentration, was evaluated. RESULTS: Rofecoxib treatment significantly increased urine osmolality due to higher urea concentrations, but reduced papillary HSP70 abundance by 50%. TUNEL staining showed numerous apoptotic cells in the papilla, associated with increased caspase-3 activity. These in vivo results were confirmed by experiments on cultured IMCD3 cells, in which COX-2 inhibition impaired the tonicity-induced up-regulation of HSP70 expression and rendered the cells susceptible to high urea concentrations. Furthermore, Delta 12-PGJ2 increased both HSP70 expression and resistance against high urea, which was causally linked to higher HSP70 levels. CONCLUSION: These observations support the view that chronic COX-2 inhibition reduces medullary HSP70 expression, thus rendering papillary cells susceptible to damage by high urea concentrations, especially when accompanied by dehydration.     

Elevated concentrations of the small stress protein HSP27 in rat renal tumors

The expression of two small stress proteins, B crystallin and the 27-kDa heat shock protein (HSP27), was studied quantitatively and immunohistochemically in normal kidney and renal tumors in rats. Levels of B crystallin in renal cell tumors tended to be higher than in normal kidney (P = 0.07), but with a wide range of values, whereas they were significantly lower in mesenchymal tumors (P < 0.0001). In contrast, HSP27 concentrations in both renal cell (mean ± SD: 1790 ± 940 ng/mg protein,n = 15) and mesenchymal (1260 ± 1080 ng/mg protein,n = 10) tumors were significantly higher than the normal kidney value (142 ± 30 ng/mg protein,n = 10,P < 0.0001). A positive correlation was found between B crystallin and HSP27 levels limited to the renal cell tumor case (Pearson's correlation coefficient,r = 0.68,P < 0.01). Immunohistochemistry revealed the loops of Henle to be positive for B crystallin, whereas HSP27 staining was positive in glomerular and interstitial vascular walls and epithelial cells of proximal and distal tubules. Positive immunostaining for B crystallin was demonstrated in six of nine renal cell tumors (67%) studied and for HSP27 in all of the nine cases (100%).     

MCP-1 and EGF renal expression and urine excretion in human congenital obstructive nephropathy

BACKGROUND: Obstructive nephropathy is characterized at the histologic level by tubular atrophy and interstitial monocyte infiltration. The molecular mechanisms underlying these histologic changes are still poorly defined. Epidermal growth factor (EGF) produced by tubular cells seems to play a pivotal role in the modulation of tubular cell growth, while monocyte chemotactic peptide-1 (MCP-1) is a powerful and specific chemotactic and activating factor for monocytes. METHODS: Twenty-four patients with congenital ureteropelvic junction obstruction [UPJO; 10 with recurrent urinary tract infection (UTI) and 10 with no UTI] and 15 healthy children were studied. Diagnosis was made by renal ultrasound, intravenous pielography, and MAG3 scan. Urinary samples were collected before and after surgery. In 10 patients, urine was also collected directly from the affected pelvis at the time of surgery. Urinary EGF and MCP-1 levels were measured by enzyme-linked immunosorbent assay. MCP-1 and EGF gene expression were evaluated by in situ hybridization in 15 biopsies from congenital UPJO and in 10 normal kidneys. RESULTS: In normal kidneys, there was a high expression of EGF mRNA, whereas MCP-1 mRNA was undetectable. MCP-1 gene expression was strikingly increased at the tubulointerstitial level in UPJO biopsies compared with controls and was directly correlated with the extent of monocyte infiltration. In addition, UPJO kidney sections showed a marked reduction in EGF gene expression that was directly correlated with the degree of tubular damage. EGF urine concentration was significantly reduced in UPJO when compared with control and directly correlated with its renal gene expression. On the other hand, the MCP-1 urine concentration was strikingly increased in UPJO patients. It is noteworthy that a significant and inverse correlation was observed between the MCP-1 concentration in the urine collected from the obstructed pelvis and the MAG3 clearance of the obstructed kidney (r = -0.76). The presence of recurrent UTI was associated with a significantly higher MCP-1 excretion and a slight reduction in EGF urine concentration. The surgical correction of UPJO was followed by an improvement of renal function together with a significant reduction in MCP-1 excretion and a marked increase in EGF urine concentrations. Interestingly, EGF urine concentration measured before surgery was significantly correlated with the difference between the MAG3 clearance of the obstructed kidney before and after surgery. CONCLUSIONS: MCP-1 and EGF seem to be involved in the pathogenesis of tubulointerstitial damage in congenital obstructive nephropathy, and their urine excretion may represent a powerful prognostic marker in this form of renal disease.     

Expression of 60-kDa and inducible 70-kDa stress proteins in gentamicin-induced acute renal failure

Background Heat shock proteins contribute to the survival of cells under stress conditions. We have previously observed the expression of HSP90 and constitutive HSP70 in rat kidneys during stress loading. This study was designed to determine whether HSP60 and HSP70i are induced in rat kidneys during exposure to gentamicin. Methods During the continuous administration of gentamicin (40 mg/kg per day) to rats for 30 days, the changes of HSP60 and HSP70i in these kidneys were quantitatively investigated by immunoblot analyses using specific antibodies. Results The indicators for renal failure,N-acetyl-β-d-glucosaminidase, blood urea nitrogen, and serum creatinine, increased, and reached the maximum levels at day 12. Thereafter, they spontaneously decreased, and were close to their normal levels at day 21, despite continued gentamicin exposure. The time course of HSP60 levels showed a unique 2-peak pattern exclusively in the cytosols of the cortex; the gentamicin target site. The second HSP60 peak occurred during the recovery phase, and coincided with published reports of a second peak of gentamicin accumulation in the kidney. The time course of HSP70i level showed a single peak at day 12 when the renal failure was most intense; the level was similar between the soluble and insoluble fractions in all portions of the kidney, except the inner medulla. Conclusion The increase in cytosolic HSP60 levels, as well as HSP70i levels, may be related to the spontaneous recovery from renal failure at the target site of the drug.     

臭氧氧化预处理对大鼠肾缺血再灌注损伤的热休克蛋白表达的影响

目的 探讨臭氧氧化预处理通过诱导热休克蛋白70(HSP70)的合成,保护大鼠肾脏缺血再灌注损伤的作用与机制.方法 建立原位大鼠单侧肾缺血再灌注动物模型,I/R前15 d经直肠吹入氧气和臭氧的混合气体5.0～5.5 ml(臭氧浓度50 mg/L,1 mg/kg体蕈,每日 1次).全自动生化分析仪检测尿素氮(BUN)、肌酐(Cr),比色法测定血清的脂质过氧化产物丙二醛(MDA)、超氧化物歧化酶(SOD).Western blot检测HSP70蛋白的含量;逆转录聚合酶链反应(RT-PCR)方法检测HSP70的表达.结果 肾缺血再灌注24 h后,血清中BUN、Cr、MDA明显增高,肾组织内HSPT0表达明显增强(P<0.05),经臭氧氧化预处理后,血清中的BUN、Cr、MDA均降低,SOD升高;HSP70表达升高更加明显(P<0.05).结论 臭氧氧化预处理可以诱导大鼠肾缺血再灌注组织中HSP70表达,减轻大鼠肾脏缺血再灌注损伤.     

Doppelniere mit Nierenbeckenabgangsstenose im Kindesalter

Laparoscopic pyeloplasty for the treatment of ureteropelvic junction obstruction (UPJO) in children is still one of the most demanding operations in urology. We report on a 12-year-old boy with UPJO in a duplicated collecting system with high ureter fissus. He was admitted with a 1-year history of recurrent flank pain and dilation of the lower duplicated collecting system. We performed a retroperitoneoscopic Anderson-Hynes pyeloplasty.     

Expression of peroxisome proliferator-activated receptor-gamma in renal ischemia-reperfusion injury

The pathogenesis of ischemia-reperfusion injury is known to involve cytokines and particularly surface adhesion molecules, the expression of which initiates the attachment of inflammatory cells. Peroxisome proliferator-activated receptor (PPAR)-gamma is considered an important immunomodulatory factor as well as a fatty acid regulator. In this study, we researched the expression of PPAR-gamma in renal ischemia-reperfusion injury of the rat. The right kidney was harvested and left renal artery and vein were clamped under laparotomy. The kidney was reperfused after 90 minutes of ischemia, and rats were sacrificed at 0, 1.5, 3, 5, 12, and 24 hours after reperfusion. PPAR-gamma expression was analyzed by immunohistochemical staining using monoclonal antibody. In normal kidney, PPAR-gamma staining was weak on endothelial cells, including mesangial cells. On the other hand, PPAR-gamma staining was weak on interstitial cells and strong on collecting ducts of medulla. From 1.5 to 5 hours after reperfusion, PPAR-gamma staining was strong on endothelial cells, moderate on interstitial cells, and strong on collecting ducts. Twelve hours after reperfusion, PPAR-gamma staining was weak on endothelial cells, moderate on interstitial cells, and strong on collecting ducts. PPAR-gamma is induced on collecting ducts, interstitial cells, and endothelial cells in a rat model having renal ischemia-reperfusion injury.     

SGP-2 expression as a genetic marker of progressive cellular pathology in experimental hydronephrosis

The onset of hydronephrosis following unilateral ureteral obstruction is associated with the induced expression of RNA and proteins encoded by the SGP-2 gene. SGP-2 expression has been shown to demarcate mammalian cells undergoing apoptosis. Using in situ hybridization, the cellular localization of SGP-2 expression in the obstructed kidney was determined as a means to study the various phases involved in the progression of hydronephrosis. Within 30 minutes of obstruction, SGP-2 mRNA expression was localized to the adventitial layers of the hilar arteries and intrarenal arterioles. Increasing time of obstruction resulted in the notable absence or depletion of this layer. In addition, the pattern of SGP-2 expression changed with time to the collecting ducts and distal tubules. This study identifies the vascular support tissue of the kidney as the initial site of reaction and potential cell death following ureteral obstruction. We believe that this observation may be of importance in explaining the early alterations in blood flow associated with hydronephrosis.     

Renal structural and functional changes after unilateral ureteral obstruction in rabbits

Renal structural and functional changes following unilateral ureteral ligation for periods of 3 days to 6 weeks were studied in rabbits. The renal pelvic pressure increased to 20 cm H2O within 3 days of obstruction and in contrast to some previous investigations it was still raised after 6 weeks. Interstitial oedema, collapse of proximal tubules and dilatation of distal tubules were the earliest observed histological changes. Later findings were interstitial fibrosis, widespread atrophy of proximal tubules and, in the latest stages, dilatation of the collecting duct system. Thus, the distal tubules appeared considerably less resistant than the collecting ducts, to the increased pressure. Renal functional changes were studied one hour after release of obstruction of 3 days, 1-2-4 or 6 weeks' duration. In comparison to the contralateral kidney a rapid decrease of blood flow and glomerular filtration occurred in spite of a normal glomerular structure and collapsed proximal tubules and were probably related to haemodynamic disturbances such as arteriolar constriction. Although absolute electrolyte excretion was much reduced, the fractional excretion of several electrolytes, especially magnesium was increased already after 3 days of obstruction. These findings can presumably be correlated to the dilatation and early epithelial alterations in the distal tubules in which magnesium is predominantly reabsorbed.