Changes in medullary glycosaminoglycan histochemistry and microvascular filling during the development of 2-bromoethanamine hydrobromide-induced renal papillary necrosis

Increased urinary uronic acid excretion in experimentally-induced renal papillary necrosis in rats

We have evaluated the potential of urinary uronic acid measurement as an early indicator in the development of renal papillary necrosis (RPN). Urinary uronic acid was quantified with a range of other urinary biochemical parameters in rats given multiple doses of N-phenylanthranilic acid (NPAA) or mefenamic acid (MFA), each of which induces a dose-related papillary necrosis. In addition, histological examination was also carried out to confirm the development and presence of RPN. NPAA was administered to male wistar rats at p.o. doses of 100, 250, and 500 mg/kg and MFA at p.o. doses of 75, 150, and 300 mg/kg on days 1-4 and 8-11, and urine samples were collected for 16 hours each day. NPAA increased uronic acid excretion two-fold for both medium and high doses from day four. MFA increased uronic acid excretion to two and a half-fold by day 10 in the highest dose administered. Urinary creatinine was equally elevated in a dose-related manner following treatment with either NPAA or MFA. None of the other routine markers (urinary or serum) of nephrotoxicity showed any statistical changes. NPAA produced a dose- and time-related increase in excretion of uronic acid. Evidence of widespread papillary necrosis was seen histologically at the high doses of NPAA or MFA. The significant elevation of uronic acid in urine following treatment with either NPAA or MFA was well ahead of the development of RPN detectable by routine histology, suggesting that uronic acid measurement could serve as an early indicator of RPN. The assessment of urinary uronic acid may therefore provide a novel sensitive and selective marker of identifying the lesion earlier than is currently possible. An increase in urinary uronic acid following NPAA and MFA treatment supports the biochemical basis of these changes as a representative of acid mucopolysaccharides accumulation.

Renal changes associated with naproxen sodium administration in cynomolgus monkeys

Naproxen sodium was administered to cynomolgus monkeys (Macaca fascicularis) by oral gavage at daily doses of 44, 88, or 176 mg/kg for 2 wk (2 monkeys/gender) or of 44 mg/kg for 13 wk (4 monkeys/gender). Body weight loss occurred in at least one monkey in all naproxen sodium-dosed groups in the 2-wk (up to 16% loss) and 13-wk (up to 22% loss) studies. Increases in plasma naproxen concentrations were dose proportional between 44 and 88 mg/kg but were less than dose proportional between 88 and 176 mg/kg. Up to 2-fold increases in creatinine and/or serum urea nitrogen values as well as higher renal weights occurred in monkeys receiving 176 mg/kg for 2 wk or 44 mg/kg for 13 wk. Microscopically, renal changes were observed in all naproxen sodium-dosed groups. Renal findings after 2 wk of exposure included increased interstitial ground substance, tubular dilatation, and tubulointerstitial nephritis; in the 13-wk study, cortical tubular atrophy and interstitial fibrosis were also observed. These studies identify the kidney as the target organ of naproxen sodium in cynomolgus monkeys.

Chemically induced analgesic nephropathy in the rat monitored by proton-electron double-resonance imaging (PEDRI)

Proton-electron double-resonance imaging (PEDRI) was used to assess renal function by monitoring the flow of the exogenous nitroxide free radical proxyl carboxylic acid (PCA) through normal and injured kidneys in the living rat. Kidney damage was induced by treatment with 2-bromoethylamine (BEA), which provides a well established model for human analgesic nephropathy. PCA clearance rates for liver, abdominal blood vessels, and renal tissues were determined from serial PEDRI images of normal rats (n = 6) and rats treated with BEA (n = 21). Different groups of BEA-treated animals were imaged on day 4 (n = 6), day 6 (n = 6), and day 9 (n = 9) after treatment. In BEA-treated rats, there was an increase in PCA half-life in all tissues studied. This increase was greatest in the kidney tissues and the effect progressed with time after treatment. The effect is probably due to BEA-induced damage to the tubules in the renal cortex and may not be related to the primary lesions in the renal medulla.

Renal papillary necrosis--40 years on

Analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) are well recognized as a major class of therapeutic agent that causes renal papillary necrosis (RPN). Over the last decade a broad spectrum of other therapeutic agents and many chemicals have also been reported that have the potential to cause this lesion in animals and man. There is consensus that RPN is the primary lesion that can progress to cortical degeneration; and it is only at this stage that the lesion is easily diagnosed. In the absence of sensitive and selective noninvasive biomarkers of RPN there is still no clear indication of which compound, under what circumstances, has the greatest potential to cause this lesion in man. Attempts to mimic RPN in rodents using analgesics and NSAIDs have not provided robust models of the lesion. Thus, much of the research has concentrated on those compounds that cause an acute or subacute RPN as the basis by which to study the pathogenesis of the lesion. Based on the mechanistic understanding gleaned from these model compounds it has been possible to transpose an understanding of the underlying processes to the analgesics and NSAIDs. The mechanism of RPN is still controversial. There are data that support microvascular changes and local ischemic injury as the underlying cause. Alternatively, several model papillotoxins, some analgesics, and NSAIDs target selectively for the medullary interstitial cells, which is the earliest reported aberration, after which there are a series of degenerative processes affecting other renal cell types. Many papillotoxins have the potential to undergo prostaglandin hydroperoxidase-mediated metabolic activation, specifically in the renal medullary interstitial cells. These reactive intermediates, in the presence of large quantities of polyunsaturated lipid droplets, result in localized and selective injury of the medullary interstitial cells. These highly differentiated cells do not repair, and it is generally accepted that continuing insult to these cells will result in their progressive erosion. The loss of these cells is thought to be central to the degenerative cascade that affects the cortex. There is still a need to understand better the primary mechanism and the secondary consequences of RPN so that the risk of chemical agents in use and novel molecules can be fully assessed.

Effect of papillotoxic agents on expression of cyclooxygenase isoforms in the rat kidney

Inhibition of renal vasodilatory prostaglandins (PGs) and secondary ischemia due to inhibition of cyclooxygenase (COX) activity has been suggested as a possible mechanism for development of analgesic-related renal papillary necrosis (RPN) in rats. Recently, it has been shown that COX exists in two related but unique isoforms, COX-1 and COX-2. It is unclear what potential roles these isoforms play in the maintenance of blood flow in the renal papilla or genesis of RPN. We evaluated the effect of 2 papillotoxic agents, including a nonsteroidal anti-inflammatory drug, indomethacin, and a chemical agent, 2-bromoethanamine hydrobromide (2-BEA), on COX-1 and COX-2 in the renal papilla as a means of assessing what changes occur in the expression of these isoforms during the development of RPN. Female Wistar rats approximately 10-17 wk old were treated with either indomethacin (75 mg/kg, single dose, or 10 mg/kg/day for 5 days) or 2-BEA (100 mg/kg/day for 4 days) to create lesions of RPN. In this study, a single 75-mg/kg dose of indomethacin did not cause light microscopic changes of RPN. However, RPN was observed in animals administered indomethacin at 10 mg/kg/day for 1 wk or 2-BEA for 5 days. The immunohistochemical analyses of kidneys showed that both COX-1 and COX-2 were present in the renal papilla of control rats. In animals treated with indomethacin (75 mg/kg), a slight to moderate decrease in both isoforms was observed in essentially normal renal papillary cells within 2 hr, that was followed by an increase in COX-2 immunoreactivity in the renal papilla, macula densa, and thick ascending limbs (both 10- and 75-mg/kg animals). This COX-2 immunoreactivity was greatest in animals with concomitant indomethacin-induced gastrointestinal injury, suggesting a possible role of inflammatory cytokines in COX-2 induction. No changes in the expression of COX isoforms in the intact papilla occurred as a result of 2-BEA; however, cells undergoing degeneration and necrosis lost immunoreactivity to both COX isoforms. The possible mechanism that leads to an initial decrease in COX immunoreactivity in indomethacin-treated animals is not known; however, a reversible ultrastructural change in the papillary cells cannot be ruled out. This decrease in COX isoforms in the renal papilla may contribute to the development of RPN through the loss of vasodilatory PGs.

Normal ultrastructure of the kidney and lower urinary tract

The mammalian urinary tract includes the kidneys, ureters, urinary bladder, and urethra. The renal parenchyma is composed of the glomeruli and a heterogeneous array of tubule segments that are specialized in both function and structure and are arranged in a specific spatial distribution. The ultrastructure of the glomeruli and renal tubule epithelia have been well characterized and the relationship between the cellular structure and the function of the various components of the kidney have been the subject of intense study by many investigators. The lower urinary tract, the ureters, urinary bladder, and urethra, which are histologically similar throughout, are composed of a mucosal layer lined by transitional epithelium, a tunica muscularis, and a tunica serosa or adventitia. The present manuscript reviews the normal ultrastructural morphology of the kidney and the lower urinary tract. The normal ultrastructure is illustrated using transmission electron microscopy of normal rat kidney and urinary bladder preserved by in vivo perfusion with glutaraldehyde fixative and processed in epoxy resin.

Evaluation of chronic oral toxicity and carcinogenic potential of lornoxicam in rats

As part of the preclinical development program for lornoxicam, a novel non-steroidal anti-inflammatory drug (NSAID), its chronic oral toxicity and carcinogenic potential was assessed in Sprague-Dawley rats. Male and female rats were administered lornoxicam by oral gavage at 0, 0.06, 0.16 or 0.40 mg/kg/day for 12 months or at 0, 0.01 or 0.06 mg/kg/day in a supplementary low-dose study of the same duration (main group: 20/sex/group; 4-wk recovery: five/sex/group; satellites for electrocardiography and toxicokinetics: five/sex/group). Drug-related toxicity mainly comprised mortality, reduced body weight gain, clinico-pathological changes indicative of anaemia resulting from blood loss, and renal damage, renal papillary necrosis and gastrointestinal mucosal lesions. The kidney-associated changes were not completely reversible during the recovery period. Toxicokinetic investigations demonstrated a dose-linear absorption of the drug. In female rats the terminal half-life was about twice that in males which led to a higher exposure of this gender to lornoxicam. A dose of 0.01 mg/kg/day was established as no-observed-effect level. In a 104-wk carcinogenicity study, lornoxicam was administered by oral gavage to male and female rats (50/sex/group) at 0 (control 1), 0 (control 2), 0.0625, 0.125 or 0.250 mg/kg/day. In females only, the high dose was reduced twice during the study due to toxicity observed (0.250 to 0.200 to 0.160 mg/kg/day). Drug-related changes were similar to those in the chronic studies and consistent with the anticipated side-effects of NSAIDs. No carcinogenic potential was revealed.

1H and 2H NMR spectroscopic studies on the metabolism and biochemical effects of 2-bromoethanamine in the rat

Male Fischer 344 rats were dosed with 2-bromoethanamine hydrobromide (BEA, N = 6) or [1,2,2,-2H4]-bromoethanamine hydrobromide (BEA-d4, N = 6) at 150 mg/kg i.p. and urine was collected -24 to 0 hr pre-dose and at 0-2 hr, 2-4 hr, 4-8 hr and 8-12 hr post-dose (p.d.). Urine samples were analysed directly using 500 and 600 MHz 1H NMR and 92.1 MHz 2H NMR spectroscopy. The major observed effect of BEA treatment was the induction of transient elevations in urinary glutaric acid (GTA) and adipic acid (ADA) excretion lasting up to 24 hr p.d. Most of the GTA was excreted in the 0-8 hr p.d. with maximal rates of 100-120 microM/hr for each rat occurring between 4 and 8 hr p.d. in animals treated with BEA or BEA-d4. GTA and ADA were shown to be of endogenous origin as there was no detectable incorporation of the 2H label into either compound following treatment of rats with BEA-d4. Following BEA-treatment there was an initial decrease in the levels of urinary citrate, succinate, 2-oxoglutarate and trimethylamine-N-oxide. A subsequent recovery of citrate and succinate was noted following the onset of medullary nephropathy. The abnormal urinary metabolite profiles were similar to that observed in the urine of humans with glutaric aciduria type II (an inborn error of metabolism) caused by a lack of mitochondrial fatty acyl coenzyme A dehydrogenases indicating that BEA or its metabolites have similar metabolic consequences. The BEA metabolite aziridine was detected by 1H and 2H NMR spectroscopy of the urine 8 hr p.d. together with BEA itself and two novel metabolites 2-oxazolidone (OX) and 5-hydroxy-2-oxazolidone (HOX). The formation of OX requires the reaction of BEA with endogenous bicarbonate followed by a cyclisation reaction eliminating HBr. Dosing rats with authentic OX resulted in the excretion of HOX but did not cause glutaric or adipic aciduria indicating that either aziridine or BEA itself was responsible for the presumed defect in mitochondrial metabolism.

Renal and urinary lipid changes associated with an acutely induced renal papillary necrosis in rats

A single dose of 2-bromoethanamine hydrobromide (BEA; 100 mg/kg body weight) given ip to male Wistar rats causes an acute renal papillary necrosis in 24 hr. Oil Red O (ORO) lipid staining is normally confined to the polyunsaturated lipid droplets of the medullary interstitial cells, but ORO-positive material was present in the endothelial cells of the vasa recta 7 hr after BEA treatment. At 24 hr (by which time papillary necrosis had developed), there were also markedly increased quantities of lipid in the cells of the collecting ducts and covering epithelia. At 48 hr totally necrosed areas stained heavily with ORO, and lipid deposits were particularly numerous in the hyperplastic urothelia adjacent to the necrosed region. Epithelial and endothelial accumulation of lipid material also extended into areas of the juxtamedulla and cortex, which appeared normal by routine haematoxylin and eosin staining. Lipid staining is more selective and sensitive for identifying papillary necrosis than routine histology, because neither hexachlorobutadiene-, aminoglycoside-, cis-platin- nor polybrene-induced lesions produce similar histochemical changes. This suggests that the capillary and epithelial deposits of lipid material are pathognomonic for the development of renal papillary necrosis. An increase in urinary triglycerides following BEA treatment supports the biochemical basis of these ORO changes as a neutral lipid accumulation.

Crystalluria, medullary matrix crystal deposits and bladder calculi associated with an acutely induced renal papillary necrosis

A single (100 mg/kg) intraperitoneal dose of 2-bromoethanamine hydrobromide induced renal papillary necrosis (RPN) acutely in rodents and caused a transient crystalluria between 4 and 8 h after dosing. These crystals comprised struvite or magnesium ammonium phosphate (MAP) as assessed by shape, solubility, infra-red spectrum and X-ray microprobe analysis. Acid-soluble, bi-refringent crystals were also present within the renal medullary matrix during the same time period as the crystalluria. The presence of the MAP was associated with loss of the anionic renal medullary mucopolysaccharides staining. A total of 5/64 rats with a 2-bromoethanamine-induced renal papillary necrosis and monitored for up to 160 days had bladder calculi that were predominantly MAP. These data suggest that medullary mucopolysaccharide matrix disruption associated with RPN leads to a release of previously bound cations, super-saturation and the nucleation of crystalline MAP. These processes could also be implicated in the formation of MAP bladder calculi.

High resolution light microscopic morphological and microvascular changes in an acutely induced renal papillary necrosis

Morphological changes were followed in semi-thin glycolmethacrylate sections, after treating male Wistar rats with a single ip dose of 2-bromoethanamine (BEA) hydrobromide (100 mg/kg) to induce renal papillary necrosis. Medullary interstitial cells had irregular nuclei at 4 hr and focal necrosis by 8 hr which spread from the papilla tip to the cortico-medullary junction from 12 hr. Increased mucopolysaccharide staining was observed in the papilla tip at 4 hr, and was lost from those regions where necrosis had developed by 48 hr. Endothelial platelet adhesion, first seen at 8 hr, was very marked at 18 hr, but affected capillaries in necrotic regions only, up to 144 hr. The absence of extravasated Monastral Blue B demonstrated the integrity of the medullary microvascular endothelia. The distal nephron showed degenerative changes at 12 hr and cell exfoliation at 18 hr. Cortical changes were confined to PAS-positive casts in the collecting duct and loop of Henle from 8 hr and dilatation of distal and proximal tubules at 8 and 72 hr, respectively. There was active repair at the junction between viable and necrotic tissue in the papilla from 24 hr with mitoses in the collecting ducts and loops of Henle. Normally the urothelium is less than 3-4 cells thick, but upper urothelial proliferation followed BEA administration. Hyperplasia was especially marked at the mouth of the ureter and in the pelvis opposite the region of necrosis (7-8 cells thick at 18 hr) and had only partially resolved by 144 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

The application of proton nuclear magnetic resonance imaging for the in vivo characterisation of chemically induced renal lesions in rats over a prolonged time study

Renal cortical and medullary spin-lattice (T1) relaxation times were measured at various time points over a period of 56 days following the administration of a single i.p. injection of 100 mg/kg 2-bromoethanamine hydrobromide (BEA), 200 mg/kg hexachloro-1,3-butadiene (HCBD) or 100 mg/kg puromycin aminonucleoside (PAN) to male Wistar rats. Administration of a single injection of HCBD caused a dramatic, immediate rise in the cortical T1 values above control values, and these levels remained elevated until, by Day 28 postinjection the levels were back to control values. Administration of BEA also caused an elevation in cortical T1 values, but in this case these values remained above control values for the rest of the study. The administration of PAN did not produce any significant increases in cortical T1 values until 14 days postinjection. The elevated T1 values remained above control values for the rest of the study. These increases observed in cortical T1 values appeared to be mirrored by decreases in medullary T1 values. Increases in cortical T1 values were accompanied by visual changes in the NMR images and enlargement of the kidneys. The histological findings were consistent with the NMR data, confirming that morphologically the tissues did show a full recovery by Day 28 in the HCBD-treated animals. This was not the case following injection of both BEA and PAN, where necrosis was not reversible and there was no recovery of the tissues.

Enzyme histochemical changes in an acutely induced renal papillary necrosis

Enzyme histochemistry was assessed in semi-thin glycolmethacrylate sections after 100 mg/kg 2-bromoethanamine (BEA) hydrobromide had been given ip to male Wistar rats to induce renal papillary necrosis. Changes in the proximal tubular marker enzymes alkaline phosphatase (Alk Phos), gamma-glutamytranspeptidase (GGT) and adenosine triphosphatase (ATPase) were not apparent before 8 hr, but there was a progressive loss up to 144 hr. The proteinaceous PAS-positive casts in the loops of Henle and the collecting ducts stained for Alk Phos and GGT (from 12 hr) and for ATPase (from 18 hr). Acid phosphatase (Acid Phos) staining was increased in the proximal tubule lysosomes from 18 hr. There was a marked increase in Alk Phos in all hyperplastic upper urothelial cells from 8 to 24 hr, and a mosaic of staining remained in the pelvis adjacent to the necrosed papilla at 144 hr. At 12 hr, there was an increase in the staining of the pelvic, ureter and bladder vascular endothelial ATPase, the intensity and area of which increased progressively from 18 hr and almost occluded the capillary lumens in the worst affected areas by 144 hr. These data show several distinct series of pathological changes after the administration of BEA. The subtle degenerative changes in the proximal tubule followed the papillary lesion, but exfoliated brush border and proximal tubular cells were important components of the protein casts in the distal nephron. Similarly, the intense Alk Phos staining in the hyperplastic regions of the upper urothelium and the increased pelvic, ureteric and bladder endothelial ATPase staining suggested they develop as a consequence of the papillary lesion.

Epidemiology and mechanistic basis of analgesic-associated nephropathy

End-stage renal failure (ESRF) due to analgesic nephropathy is still a common clinical condition in several countries, but the prevalence in dialysis patients shows large geographical differences. The frequency of ESRF of unknown aetiology is the inverse of that linked to analgesic abuse, and data suggest that the occurrence of analgesic nephropathy may be underestimated. The study of analgesic nephropathy is difficult because the earliest damage to the kidney is a renal papillary necrosis (RPN), which cannot easily be diagnosed. Continued analgesic abuse generally leads to a progressive secondary cortical degeneration which is easier to diagnose. If analgesic abuse is stopped at an early enough stage in nephropathy, clinical symptoms stabilize or improve, and ESRF may be averted. A high incidence of upper urothelial carcinoma (UUC) is also observed in individuals with a history of analgesic abuse, but it is still not clear if the two have a related pathogenesis. Study of the mechanism of RPN in animals administered analgesics and nonsteroidal antiinflammatory drugs (NSAID) has been difficult owing to their extrarenal toxicity. Several model compounds cause identical clinical changes and have as their selective target the renal medullary interstitial cells; subsequently, other changes (including cortical and glomerular degeneration) develop as a secondary cascade. A number of mechanisms have been proposed to explain RPN (e.g., counter-current concentrating mechanism, ischaemic injury, altered prostaglandin metabolism, immunological changes), but peroxidative metabolism of papillotoxic chemicals within the interstitial cells seems to be the most likely cause. Analgesic abuse is a costly socioeconomic condition for which there is currently no clinical treatment. If it is diagnosed early enough, severe renal degeneration can be prevented. Additional epidemiological information is needed to establish the causative role of analgesics and other chemicals, in order to determine the relative risk of each. Additional animal experiments are needed in order to clarify the molecular pathogenesis of RPN and UUC, to differentiate the stages in progression to ESRF and to develop more sensitive and selective diagnostic criteria.

Glycosaminoglycans of the rat renomedullary interstitium: ultrastructural and biochemical observations

The rat renal papillary interstitum which contains abundant proteoglycans is a unique area important in renal function. These proteoglycans were studied ultrastructurally by ruthenium red fixation and staining and phosphate-buffered fixation before and after enzyme digestion. A tissue culture of rat renomedullary interstitial cells, the predominant cell of the renal papillary interstitum, was studied for its ability to synthesize proteoglycans and the proteoglycans were then analyzed. Tissue slices of whole rat renal inner medulla were also evaluated for their synthetic ability. In combination, these studies indicate that the dominant glycosaminoglycan is hyaluronic acid. The tissue culture of rat renal medullary interstitial cells synthesized glycosaminoglycans and on analysis, hyaluronic acid was found to be the chief glycosaminoglycan secreted by the renomedullary interstitial cells. Combined with the removal of the proteoglycans from tissue by leech hyaluronidase and testicular hyaluronidase, this suggests that the dominant glycosaminoglycan is hyaluronic acid. Hyaluronic acid is also synthesized by the intact papilla confirming the findings with the tissue culture. However, in addition, sulfated glycosaminoglycans were also synthesized by the intact papilla, presumably the product of the noninterstitial components of the papilla.

Nephrotoxicity: a rational approach to target cell injury in vitro in the kidney

1. The kidney is a complex organ in which there is cellular heterogeneity. Many nephrotoxic chemicals target preferentially for discrete cell types, but adjacent, morphologically different cells are unaffected. This selectivity has made the assessment of nephrotoxicity in vivo (and the study of underlying mechanisms) difficult. Discrete renal injury can, however, be exploited in vitro, to study the interactions between the toxic compound and the target cell. 2. Several in vitro models have been used to study the potential interaction between the target cells and chemicals, including perfusion of the isolated kidney, renal slices, freshly isolated fragments, primary cultures and continuous cell lines. Where appropriate, isolated organelles and purified enzymes can also be used. 3. The target cell toxicity in vivo of adriamycin, 2-bromoethanamine and hexachlorobutadiene N-acetyl cysteine conjugate is selectively maintained towards glomerular epithelial, medullary interstitial and proximal tubular cells, respectively, in vitro, showing that the "in vivo-in vitro gap" can be bridged. Characteristics unique to each of these renal cell types, such as the selective uptake of a toxin, enzyme systems for generating biologically reactive intermediates, and the presence of lipid droplets (rich in polyunsaturated fatty acid) and peroxidase activity have been identified, and one or more of these may explain the mechanisms of selective injury in discrete regions of the kidney.

The mechanisms of target cell injury by nephrotoxins

Hexachlorobutadiene-N-acetylcysteine (HCBD-NAC), adriamycin and 2-bromoethanamine hydrobromide are three renal toxins that have shown in vivo a highly selective target cell toxicity--to the proximal tubules, the glomerular epithelial cells and the medullary interstitial cells, respectively. To study some aspects of the mechanisms of this selective toxicity, the three types of target cell were isolated from the kidneys of Wistar rats, and cultures of the cells or tissue fragments were exposed to various concentrations of the three toxins. Using fluorescence microscopy combined with enzyme and histochemical probes, the selective target-cell toxicity of the three compounds already established in vivo was demonstrated also in vitro. Moreover, the in vitro toxic effect of HCBD-NAC was ameliorated by probenecid, as is the case in vivo. Several functional characteristics specific to each of the target cells, such as the selective uptake of a toxin, the presence of lipid droplets and the level of peroxidative enzyme activity, have been identified as probable factors in the occurrence of the target cell necrosis.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 1

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 2

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

The effect of N-phenylanthranilic acid-induced renal papillary necrosis on urinary acidification and renal electrolyte handling

The oral administration of a suspension of N-phenylanthranilic acid (N-PAA), over the range of 0.5 to 2 mmol/kg for 14 consecutive days, caused a dose-related renal papillary necrosis (RPN), which involved no more than 30% of the medullary apex. This area of necrosis was no greater following daily doses of 3 and 5 mmol/kg of N-PAA for 14 days, but cortical degenerative changes were induced. The area of the necrotic lesion was greater in the left kidneys of individual rats than in the right kidneys. The apex-limited histopathological changes associated with the administration of low doses of N-PAA were not reflected by altered electrolyte or water homeostasis and only high doses of N-PAA caused significant changes. Urinary volume was significantly increased (in animals treated with 5 mmol/kg), whereas urinary osmolality (greater than 2 mmol/kg N-PAA), and Na+ (5 mmol/kg), K+ (5 mmol/kg), and Cl- (5 mmol/kg) excretion was decreased compared to controls. Blood urea nitrogen was increased at doses greater than 3 mmol/kg in association with cortical degenerative changes. When untreated rats were dosed orally with NH4Cl (400 mg/kg) there was a lag period between 0 and 2 hr (when no changes in H+ excretion occurred), but the urinary pH was depressed in the 2- to 4-hr collection period. Only those rats treated with the highest dose of N-PAA (5 mmol/kg) showed a significantly impaired urinary acidification after NH4Cl loading. There was, however, a statistically significant dose-related decrease in the excretion of Cl- following NH4Cl dosing, provided urine was sampled between 0 and 2 hr. These data highlight the failure of the commonly used renal function tests (such as urinary volume, osmolality, and electrolyte excretion) to reflect apex-limited RPN, unless cortical degenerative changes were also present. The dose-related depression of Cl- excretion in the 0- to 2-hr period following oral NH4Cl loading, suggests that appropriately timed sampling of this urinary anion could offer an improved criterion for the diagnosis of RPN.