Insulin-like growth factor-1 enhances epidermal growth factor receptor activation and renal tubular cell regeneration in postischemic acute renal failure

Growth factors such as insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), and hepatocyte growth factor have been shown to accelerate the recovery from postischemic acute renal failure (ARF) with a concomitant increase in DNA synthesis. Interactions between growth factors have been demonstrated in a number of in vitro studies. This study examined the effect of exogenous IGF-1 on the DNA synthesis and EGF receptor (EGF-R) activation in postischemic rat kidneys. Thirty minutes after the relief of 30-minute total occlusion of the left renal artery in anesthetized 225 to 300 gm Sprague-Dawley rats, either IGF-1 (75 micrograms/kg) or normal saline solution (NS, 0.2 ml) was given by intravenous bolus, followed by twice daily subcutaneous injections of IGF-1 (50 micrograms/kg) or 0.2 ml NS for 4 days, respectively, in IGF-1-Tx) and NS treated (NS-Tx) groups (n = 8 each). On the day after the completion of treatment, inulin clearance (ml/kg/min) of the postischemic kidneys in the IGF-1-Tx group was significantly higher (p < 0.01) than inulin clearance of kidneys in the NS-Tx group. This was associated with improved kidney morphology. IGF-1 treatment also enhanced the labeling index of 5-bromo-2'-deoxyuridine (percent of stained tubule cells), a marker for active DNA synthesis, in the outer medulla of postischemic kidneys at 1 day and 2 days after the injury. EGF-R tyrosine phosphorylation (which reflects receptor activation) increased in postischemic kidneys in both NS-Tx (n = 5) and IGF-1-Tx (n = 3) groups 1 day after the injury as compared with nonischemic contralateral kidneys. In the IGF-1-Tx group there was also increased iodine 125-labeled EGF binding and EGF-R protein. Our results demonstrate a beneficial effect of IGF-1 on postischemic ARF. Furthermore, they suggest that EGF-R activation is involved in tubular regeneration and that IGF-1 may enhance EGF-R activation by increasing EGF-R expression.

Morphological classification of renal cancer

The current classification of renal-cell adenomas (RCAs) and carcinomas (RCCs) is based on eight basic cell and tumor types (entities) with characteristic morphologic features: (1) RCCs of clear-cell type, (2) RCAs/RCCs of chromophilic-cell type, (3) RCAs/RCCs of chromophobic-cell type, (4) RCCs of duct Bellini type, (5) RCCs of transitional-cell type, (6) RCCs of neuroendocrine type, (7) RCAs of oncocytic type, and (8) RCAs of metanephroid type. Tumors with a proposed histogenesis from the proximal tubule (clear-cell and chromophilic tumors) amount to 85% of renal cancers, whereas tumors with a proposed histogenesis from the connecting tubule/collecting duct (chromophobic-, oncocytic-, and duct Bellini-type tumors) amount to only 11%. The remaining tumor types represent rare entities (less than 1% each). Tumor cytogenetics data confirm the proposed eight morphologic subtypes and give further indications for type-specific tumor development and progression.

Calcium oxalate crystal interaction with renal tubular epithelium, mechanism of crystal adhesion and its impact on stone development

The interaction between renal epithelial cells and calcium oxalate (CaOx) crystals and/or oxalate ions plays a critical role in the formation of urinary stones. Epithelial cells respond to hyperoxaluria and the presence of CaOx crystals in the kidneys by increased enzymuria and internalization of the crystals. Crystal cell interaction results in movement of crystals from the luminal to the basolateral side between the cells and the basement membrane. Once beneath the epithelium, crystals adhere to the basement membrane and become anchored inside the kidneys. Crystals anchored to basement membrane of the peripheral collecting duct aggregate with other crystals and move through an eroding epithelium to the papillary surface, furnishing an encrustation platform or a nidus for future development of a kidney stone. Thus interaction between renal epithelial cells and CaOx crystals and/or oxalate ions is an essential element in the development of urinary stone disease.

[Tumors of the Bellini collecting tubules. Apropos of a case]

Based on a personal case and a review of the literature, the authors describe the particular features of renal tumours arising from the papillary ducts of Bellini. The most remarkable feature of this rare lesion, which has a very poor prognosis, is that it arises in the medullary zone of the kidney. The histological diagnosis is often difficult to confirm and immunohistochemical techniques are essential. The possible role of adjuvant chemotherapy following nephrectomy and the type of regimens used are discussed.

Renal medullary carcinoma associated with sickle cell trait: radiologic findings

PURPOSE

To correlate the radiologic and pathologic findings in patients with renal medullary carcinoma and sickle cell trait.

MATERIALS AND METHODS

Radiologic studies of five pathologically proved cases of renal medullary carcinoma were retrospectively correlated with gross pathologic findings. Excretory urograms, computed tomographic (CT) scans, sonograms, photographs of the gross surgical specimens, and an angiogram were available for review. Each case was analyzed for tumor location, pattern of growth, contrast enhancement and echotexture, angiographic pattern, and stage.

RESULTS

All tumors arose centrally within the kidney, grew in an infiltrative pattern, and invaded the renal sinus. Caliectasis without pelviectasis was present in three cases. Contrast enhancement and echotexture were heterogeneous in all patients. Tumor necrosis with communication into the collecting system occurred in one patient. The one available angiogram demonstrated hypovascularity.

CONCLUSION

Patients with renal medullary carcinoma share particular demographic, clinical, and radiologic features that might enable radiologists to suggest a specific diagnosis.

Functional and morphological aspects of thallium-induced nephrotoxicity in rats

Until now the effect of thallium (Tl) on renal function has not been investigated systematically. Therefore, the dose (5, 10, 15, 20 mg Tl2SO4/kg body wt., intraperitoneally) and time-dependence of renal damage was investigated in diuresis experiments on conscious rats. Morphology was evaluated after perfusion fixation in situ. Morphologic changes were localized in the thick ascending limb of the loop of Henle, mostly expressed at the 2nd day after Tl administration, which were completely normalized again at the 10th day. Other parameters such as Tl concentration, changes in water content and the activity of Na+/K(+)-ATPase as well as the diuretic effect of furosemide confirmed the Tl effect to be localized in the renal medulla. One single Tl administration is followed by a decrease in glomerular filtration rate (GFR) and urine volume and an increase of proteinuria. Electrolyte excretion was only slightly changed. All changes were reversible within the 10-day investigation period.

USPIO-enhanced MR imaging of glycerol-induced acute renal failure in the rabbit

Enhanced-MR imaging in combination with ultrasmall superparamagnetic iron oxide (USPIO) was used in the glycerol-induced model of acute renal failure (ARF) in the rabbit to detect renal perfusion abnormalities. A control group (n = 5) and an ARF group (n = 5) were studied after intramuscular injection of glycerol (10 ml/kg) with T2-weighted spin-echo sequence at 1.5 T and a 27 mumol/kg IV dose of iron. The signal intensity (SI) was quantified in the cortex, the outer medulla (OM), and the inner medulla (IM). In control rabbits, the maximum SI decrease after USPIO injection was in the OM (76% +/- 3.6), as this is the region of maximal vascular density, then in the IM (73.4% +/- 2.9). In the glycerol group, SI loss in the OM (61% +/- 12.6) and the IM (45.2% +/- 16.24) was significant less than in the control group (p < .05). Pathology results showed fibrinous thrombus in the efferent arterioles and congestive aspect of the vasa recta in the medulla. We argue that a reduced medullary concentration of USPIO in the renal failure group is indicative of medullary hypoperfusion.

Franz Volhard Lecture. Evolution of the medullipin concept of blood pressure control: a tribute to Eric Muirhead

The medullipin system discovered by the late Eric E. Muirhead is a feedback blood-pressure control system operating from the renal medulla. In contrast to the renin-angiotensin system, which upregulates pressure, the medullipin system downregulates blood pressure. THE MECHANISM: A rise in arterial pressure has two important consequences. First, medullary blood flow increases, renal interstitial fluid pressure rises and there is a reduction in the medullary urea osmotic gradient. Second, secretion of medullipin I is increased, which circulates to the liver, where it is converted to the active hormone, medullipin II, by a P-450 cytochrome oxidase pathway. Both of these mechanisms work in parallel to reduce arterial pressure with an increase in the urinary excretion of sodium and water coupled with systemic arterial vasodilation by medullipin II.

In vivo and in vitro detachment of proximal tubular cells and F-actin damage: consequences for renal function

We investigated the relationship between F-actin damage and cell detachment using nephrotoxic L-cysteine S-conjugates. In vivo S-(1,2-dichlorovinyl)-L-cysteine (DCVC) induced loss of F-actin in the S3 segment of the proximal tubule in the outer stripe of the outer medulla, which was associated with loss of the brush border and loss of cells from the basement membrane. In vitro DCVC caused the detachment of primary cultured rat renal proximal tubular cells (PTC), which was clearly associated with F-actin damage. Disorganization of F-actin correlated with an increase in cellular levels of G-actin, indicating depolymerization of F-actin. Cell detachment was preceded by a complete loss of the alpha-actinin binding protein talin from the focal adhesions, which was directly associated with F-actin disorganization. Inhibition of formation of highly reactive metabolites from L-cysteine S-conjugates by L-cysteine-S-conjugate beta-lyase completely prevented both F-actin damage and cell detachment by DCVC. Although inhibition of DCVC-induced lipid peroxidation and reduction of intracellular free calcium by N,N'-diphenyl-p-phenylenediamine and the acetoxymethyl ester of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, respectively, clearly prevented cell death, no protection was observed against the DCVC-induced F-actin disorganization, talin redistribution, and cell detachment. Also, F-actin damage was unrelated to changes in the energy status of the PTC, since cellular ATP content was unaffected. The data clearly demonstrate a close relationship between F-actin damage, disturbances of focal adhesions, and cell detachment. In addition, different molecular pathways are involved in the cell detachment caused by F-actin disorganization and initiation of cell death.

Tubular basement membrane changes during induction and regression of drug-induced polycystic kidney disease

Defective cell-extracellular matrix (ECM) biophysiology is considered a factor in the development of polycystic kidney disease (PKD). Altered biosynthesis of various ECM components may result in tubular dysmorphogenesis and uncontrolled tubular cystic expansion. In this study, expression of certain ECM components was investigated in a diphenylthiazole (DPT)-induced rat model of PKD. DPT induces cystic change in all the collecting tubules, most severe in the outer medulla and inner cortex, and following withdrawal of DPT, cystic tubules return to normal with persistence of focal interstitial fibrosis. SDS-PAGE analyses of isolated tubular basement membranes (TBMs) of control and PKD kidneys revealed overall similar electrophoretic migratory bands. However, in PKD, there were relative increases in components with M(r) approximately 380,000, 250,000 and 145,000, and a decrease in the component with M(r) approximately 55,000. Immunoblot analyses revealed that the major components of TBM (type-IV collagen, laminin beta 1 and beta 2 chains and entactin) were present in the same relative concentrations in control and PKD. The expression of tubulointerstitial (TIN) antigen was decreased. Also, the relative concentrations of type-I collagen and fibronectin were increased in the PKD group. Following recovery, the expressions of TIN and fibronectin returned to normal, whereas type-I collagen remained elevated. ELISA determinations revealed increased expression of interstitial collagens type-I, -V and -VI in PKD vs control and they remained elevated following recovery, while that of type-III was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical characterisation of probable intravascular haematopoiesis in the vasa rectae of the renal medulla in acute tubular necrosis

Immunohistochemistry was applied to identify the nature of the nucleated cells that accumulate in the vasa rectae of the corticomedullary junction in acute tubular necrosis. In all 6 cases studied, there were intravascular cells that reacted with monoclonal antibodies to erythroblast, macrophages, myeloid cells, T and B lymphocytes and rare megakaryocytes. The findings are consistent with the occurrence of intravascular haematopoiesis in the renal medulla in acute tubular necrosis.

Presence and distribution of endothelin-1 gene expression in human kidney

To investigate the presence and the distribution of preproendothelin-1 (prepro-ET-1) mRNA in human kidney, eight human kidneys obtained at surgery from patients affected by localized renal tumors were studied. Northern blot analysis using a human prepro-ET-1 cDNA probe labeled with 32P showed the presence of a single band of approximately 2.3 kb that was present both in the renal cortex and medulla of all the kidneys studied. Densitometric analysis of hybridization signals demonstrated that prepro-ET-1 mRNA levels in the renal medulla were 2.2-fold higher than those in the renal cortex. The distribution of prepro-ET-1 mRNA in human kidney was investigated by in situ hybridization using a human prepro-ET-1 RNA probe labeled with 35S. The greatest density of prepro-ET-1 mRNA was observed in the renal medulla, where hybridization signal was demonstrated in vasa recta bundles and capillaries and in collecting ducts. By combining in situ hybridization with immunohistochemical detection of von Willebrand factor, we demonstrated that 93 +/- 2.5% of nontubular medullary cells containing prepro-ET-1 mRNA were endothelial cells. In the cortex, prepro-ET-1 mRNA was localized in the endothelial layer of arcuate and interlobular arteries and veins and in the endothelial cells of afferent arterioles. The results of the present study demonstrate that ET-1 gene expression is present in vascular and tubular structures of the human kidney. It is possible that ET-1 synthesized locally in the human kidney represents a local system affecting renal hemodynamics and functions through paracrine and/or autocrine actions on different renal structures.

Asymmetrical atrophy of the renal medulla: a previously unreported abnormality

Investigation of the smaller of a pair of unequal kidneys showed a band of atrophy in the inner medulla, sparing the papillary tip, which was viable and contained collecting ducts. The kidney had extensive cortical atrophy with glomerulocystic disease and multiple tiny renal cell neoplasms. These changes were considered secondary to the medullary lesion. Study of 85 other kidneys taken a autopsy and surgery showed 8 other cases with similar band-like atrophy in the medulla to various degrees. All 9 cases had severe vascular disease. This asymmetrical or band-like atrophy of the renal medulla seemed to be fairly common but previously unreported, could be differentiated from renal papillary necrosis, and was most likely due to an episode of severe ischaemia, possibly in kidneys with pre-existing vascular narrowing.

Nitric oxide and prostanoids protect the renal outer medulla from radiocontrast toxicity in the rat

Human radiocontrast nephrotoxicity is predicted by the presence of multiple risk factors, often associated with compromised renal circulation. To produce a simple model of radiocontrast nephropathy, rats were pretreated with indomethacin and N omega-nitro-L-arginine methyl ester (L-NAME, to inhibit nitric oxide synthesis) before the administration of iothalamate. Acute renal failure consistently developed, with a decline in creatinine clearance from 1.05 +/- 0.10 to 0.27 +/- 0.05 ml/min (P < 0.001) associated with selective necrosis of 49 +/- 9% of medullary thick ascending limbs. Hemodynamic studies using laser-Doppler probes revealed that when injected alone, iothalamate increased outer medullary blood flow to 196 +/- 25% of baseline (P < 0.001). Pretreatment by L-NAME or indomethacin both reduced basal medullary blood flow and transformed the medullary vasodilator response to radiocontrast into vasoconstriction, with a prolonged reduction of medullary blood flow to less then half of baseline. Combined administration of indomethacin, L-NAME, and iothalamate lowered medullary blood flow to 12 +/- 4% of baseline. We conclude that prostanoids and nitric oxide have an important protective role in the renal response to radiocontrast material. Reduced synthesis of these vasoactive substances in renal/vascular diseases may predispose patients to radiocontrast nephropathy.

Chronic renal disease and papillary necrosis associated with the long-term use of nonsteroidal anti-inflammatory drugs as the sole or predominant analgesic

The risk of renal papillary necrosis and renal dysfunction due to the chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) is unknown. In a prospective study of 259 heavy analgesic users seen in a general medical hospital over an 11-year-period beginning in January 1982, 69 new cases of analgesic nephropathy with renal papillary necrosis were confirmed by intravenous urogram (26.6%), ultrasonography (30.4%), and/or computed tomography (43%). Twenty-nine of these patients (42%) had consumed excessive quantities of NSAIDs alone; an additional nine patients (13%) had consumed NSAIDs predominantly in combinations with paracetamol, aspirin, phenacetin, caffeine, and/or traditional herbal medications. Of those patients who consumed NSAIDs alone, 17 had consumed only a single type of NSAID and the remaining 12 had consumed multiple types of NSAIDs. The amount of NSAIDs administered ranged from 1,000 to 26,600 capsules or tablets over a 2- to 25-year period. Renal impairment (serum creatinine, 126 to 778 mumol/L) was noted in 26 of these 38 patients (64.8%). The reasons given for consuming NSAIDs include gouty arthritis (18 patients), osteoarthritis (seven patients), rheumatoid arthritis (six patients), chronic headache (three patients), gouty arthritis plus chronic headache (three patients), and chronic backache (one patient). All patients were prescribed these drugs and were followed medically. The occurrence of analgesic nephropathy was predominantly in males (male to female ratio, 1.9:1). Most of the patients did not have the characteristic psychological profile attributed previously to analgesic abuse nephropathy. Associated addictive habits, such as the use of psychotropic drugs and sleeping tablets, purgative abuse, and alcoholism, were absent.(ABSTRACT TRUNCATED AT 250 WORDS)

L-651,392, a potent leukotriene inhibitor, controls inflammatory process in Escherichia coli pyelonephritis

In this study, the relationship between leukotrienes, peritubular cell infiltration with polymorphonuclear cells (PMNs) and renal tubular damage was investigated in a rat model of acute ascending pyelonephritis. Infection was induced by the injection of 10(5) CFU of Escherichia coli into the bladder and occlusion of the left ureter for 24 h. Treatment of infected animals was started 24 h after the induction of pyelonephritis with either hydrocortisone (25 mg/kg of body weight per day), the leukotriene inhibitor L-651,392 (10 mg/kg/day), or the vehicle of L-651,392 and was maintained for 5 days. At the end of treatment, the animals were killed, serum was collected, and both kidneys were removed for colony counts and histopathology. Renal function was evaluated by the measurement of blood urea nitrogen levels and creatinine clearance. The numbers of PMNs and mononuclear cells (MNs) in the cortex and medulla were recorded for all groups on plastic sections done from the left kidney. Infection alone (vehicle of L-651,392) resulted in intensive interstitial infiltration and a severe tubular destruction in the cortex. Treatment with hydrocortisone did not prevent PMN migration and tissue damage. By contrast, treatment with L-651,392 resulted in a significant reduction in PMNs (P < 0.001 in comparisons with all other groups) and greater preservation of the tubular structure despite identical bacterial counts than in the group receiving hydrocortisone. We conclude that L-651,392 prevents inflammatory cells from reaching the site of infection and protects the kidney from tubular damage associated with inflammation during pyelonephritis. Inhibitors of leukotrienes should be further investigated for their potential benefit as adjuvants to antibiotherapy in the treatment of pyelonephritis.

Renal parenchymal abnormalities associated with renal vein thrombosis: correlation between MR imaging and pathologic findings in rabbits

OBJECTIVE

The purpose of this study was to correlate abnormalities of the renal parenchyma seen on MR images with pathologic findings in rabbits with acute thrombosis of the renal vein.

MATERIALS AND METHODS

MR images were obtained in 21 rabbits before and 1 hr to 2 weeks after ligation of the renal vein. MR findings were correlated with pathologic findings.

RESULTS

The cross-sectional area of the kidney was 1.7, 1.8, 1.9, 2.2, 1.3, and 1.0 times of its initial size at 1 hr, 3 hr, 1 day, 3 days, 1 week, and 2 weeks, respectively, after ligation of the renal vein. Corticomedullary contrast on T1-weighted images decreased persistently from 1 hr to 2 weeks after ligation. Between 1 hr and 1 week after ligation, T2-weighted images showed a layer with low signal intensity that was correlated with medullary congestion and hemorrhage on pathologic specimens.

CONCLUSION

MR images show a layer with low signal intensity in the renal medulla that probably represents medullary congestion and hemorrhage of the kidney in rabbits with acute thrombosis of the renal vein.

Acute hypoxia and endogenous renal endothelin

Endothelin (ET) is a potent vasoconstrictor peptide of endothelial cell origin. Recent studies have suggested a nonvascular paracrine and/or autocrine role for endothelin in the kidney. This study was designed to elucidate the renal ET response to acute moderate hypoxia, as reflected by urinary ET excretory rate and renal tissue ET immunoreactivity, and to correlate these responses to the hemodynamic and excretory changes during hypoxia. Experiments were conducted in two groups of anesthetized dogs: hypoxic group (10% O2 ventilation: PO2, 44 mm Hg; N = 7) and time control group (room air ventilation: PO2, 111 mm Hg; N = 6). After 60 min of hypoxia or room air ventilation, kidneys were harvested and stained immunohistochemically for ET. Acute moderate hypoxia was associated with significant increases in urinary ET excretion, urine flow, urinary sodium excretion, and fractional excretion of sodium (P < 0.05). There was no significant change in GFR, RBF, renal vascular resistance, or mean arterial pressure. Renal immunohistochemistry for ET revealed increased staining in the proximal and distal tubules in the hypoxic group as compared with controls. This study demonstrates that acute moderate hypoxia results in increased urinary ET excretion and renal tubular ET immunoreactivity, in association with diuresis and natriuresis, and suggests a nonvascular role of endogenously produced renal ET in the regulation of sodium homeostasis during hypoxia.

Measurement of renal transit of gadopentetate dimeglumine with echo-planar MR imaging

Times of peak gadolinium concentration ([Gd]) after intravenous (IV) and left ventricular (LV) bolus injection of gadopentetate dimeglumine were determined in renal cortex and medulla in normal rabbits and in rabbits after saline load (overhydration) or hemorrhage (dehydration). Magnetic resonance images were obtained with echo-planar inversion-recovery sequences, and signal intensity-versus-time curves in cortical and medullary regions of interest were converted to [Gd]-versus-time curves. Cortical perfusion measured with microspheres demonstrated that the three physiologic states were significantly different. There were three separate [Gd] peaks in both the cortex and medulla as the bolus moved from one anatomic compartment to the next. The first cortical peak occurred sooner after LV than after IV bolus injection (P < .05) and later in dehydrated than in normal and overhydrated rabbits (P < .05). The first medullary peak always followed the first cortical peak by about 6-10 seconds and mirrored the cortical patterns. The second and third cortical peaks were consistent with proximal and distal tubular transit. These peaks similarly showed faster response to LV than IV injection and were delayed by hemorrhage. The authors conclude that quantitative physiologic information can be obtained with dynamic contrast-enhanced MR imaging of the kidney.

[The contribution of endoscopy in the diagnosis of unilateral hematuria of renal origin and pseudotumors of the upper urinary tract]

From 1985 to 1992, 9 patients (6 males, 3 females) with a mean age of 47 years, presenting with a clinical picture suggestive of a tumour of the upper urinary tract (haematuria and/or pelvic or caliceal radiolucent filling defect), underwent retrograde (6 cases) and/or percutaneous (9 cases) endoscopic exploration of the upper urinary tract. The percutaneous examination allowed a precise diagnosis and appropriate treatment adapted to the lesion detected (papillary necrosis: 2 cases; ectopic papilla: 2 cases; hypertrophy of Brunn's nests: 1 case; papillary angioma: 1 case; haemorrhagic papillitis: 3 cases) in every case. Endoscopic exploration of radiolucent lesions of the upper tract and unexplained renal haematuria is therefore justified whenever the diagnosis of upper tract tumour is uncertain on the basis of the radiological and cytological assessment.

Giant renomedullary interstitial cell tumor

We report a case of a tumor of the renal medulla. Tumor cells were characteristic of renomedullary interstitial cells as demonstrated by light microscopy, immunohistochemistry and electron microscopy. Such masses are usually small (less than 0.5 cm.) and incidental. This neoplasm, however, was 5.0 cm. in diameter. To our knowledge, our case is unique because of tumor size and because it is the first report of an interstitial cell tumor of the kidney that has been clinically observed and surgically excised.