Acute nephrotoxicity of N-phenyl and N-(monochlorophenyl) succinimides in Fischer 344 and Sprague-Dawley rats

Nephrotoxicity induced by C- and N-arylsuccinimides

The succinimide ring is incorporated into hundreds of compounds that are widely used as agricultural, industrial, and pharmaceutical agents. Some succinimide derivatives that contain an aryl group on the ethylene bridge of the succinimide ring (C-arylsuccinimides) or on the nitrogen atom (N-arylsuccinimides) induce nephrotoxicity in humans and/or laboratory animals. Acute toxicity induced by this general class of compounds is typically characterized as polyuric renal failure, while chronic nephrotoxicity is seen as chronic interstitial nephritis. In this review, the structure-nephrotoxicity relationships, biotransformation, and mechanisms of nephrotoxicity for the C- and N-arylsuccinimides are examined.

Nephrotoxic and hepatotoxic potential of imidazolidinedione-, oxazolidinedione- and thiazolidinedione-containing analogues of N-(3,5-dichlorophenyl)succinimide (NDPS) in Fischer 344 rats

Nephrotoxicity of the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) in rats is believed to involve metabolism on the succinimide ring. To further investigate this hypothesis, we synthesized and tested the following NDPS analogues, which contain other cyclic imide rings and may therefore be metabolized differently than NDPS: 3-(3,5-dichlorophenyl)-2,4-oxazolidinedione (DCPO), 3-(3,5-dichlorophenyl)-2,4-imidazolidinedione (DCPI), 3-(3,5-dichlorophenyl)-1-methyl-2,4-imidazolidinedione (DCPM) and 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT). Male Fischer 344 rats were administered DCPO, DCPI, DCPM, DCPT (0.6 or 1.0 mmol/kg, i.p. in corn oil), NDPS (0.6 mmol/kg, i.p. in corn oil) or corn oil (4 ml/kg). As evidenced by diuresis, proteinuria, elevated blood urea nitrogen levels, increased kidney weights and proximal tubular damage, NDPS produced severe nephrotoxicity in the rats. In contrast, DCPO, DCPI, DCPM and DCPT were mild nephrotoxicants. None of the compounds elevated serum alanine transferase activity or liver weights in the rats, however DCPT produced centrilobular necrosis. These experiments confirm that NDPS-induced nephrotoxicity is critically dependent on the presence of the succinimide ring. Furthermore, replacement of the succinimide ring with a thiazolidinedione ring produced a more pronounced effect on the liver than on the kidney. Liver damage has been reported in type II diabetic patients taking troglitazone, rosiglitazone and pioglitazone. Since these compounds also contain a thiazolidinedione ring, DCPT may be useful for investigating the role of this structural feature in hepatotoxicity.

Nephrotoxic potential of N-(3,5-dichloro-4-fluorophenyl)succinimide in Fischer 344 rats: comparison with N-(3,4,5-trichlorophenyl)succinimide

Numerous structure-nephrotoxicity relationship studies from our laboratory have demonstrated that N-(3,5-dichlorophenyl)succinimide (NDPS) is one of the most potent nephrotoxicants among the N-arylsuccinimides. The purpose of this study was to extend our previous structure-nephrotoxicity relationship studies by examining the effect of addition of a fluoro verses a chloro group at the 4-phenyl position in NDPS. Male Fischer 344 rats (four rats/group) received a single intraperitoneal (i.p.) injection of N-(3,5-dichloro-4-fluorophenyl)succinimide (NDCFPS) or N-(3,4,5-trichlorophenyl)succinimide (NTCPS)(0.4 or 0.8 mmol/kg) or vehicle, and renal function monitored at 24 and 48 h. NDCFPS did not induce significant nephrotoxicity at either dose tested. In contrast, NTCPS (0.4 or 0.8 mmol/kg) induced marked nephrotoxicity characterized by diuresis, increased proteinuria, glucosuria, elevated kidney weight and increased blood urea nitrogen (BUN) concentration. NTCPS also induced marked proximal tubular necrosis at both doses tested. Neither NDCFPS nor NTCPS induced hepatotoxicity at either dose tested. The results of these experiments indicate that addition of a fluoro group at the 4-position on the phenyl ring of NDPS produces a nonnephrotoxicant NDPS derivative (NDCFPS), while addition of a chloro group at this site produces an NDPS derivative with similar nephrotoxic potential to NDPS. The mechanism for this differential effect between 4-halophenyl substitution is unclear, but may result from increased hydrolysis of the succinimide ring and/or increased clearance of N-arylsuccinimide metabolites when a fluoro group is added to the 4-position of the phenyl ring.

The effect of aromatic fluorine substitution on the nephrotoxicity and metabolism of N-(3,5-dichlorophenyl)succinimide in Fischer 344 rats

N-(3,5-Difluorophenyl)succinimide (DFPS) is a non-toxic analogue of the nephrotoxic fungicide N-(3,5-dichlorophenyl)succinimide (NDPS). Although NDPS must be metabolized to produce renal damage, the metabolic fate of DFPS is unknown. These studies were therefore designed to examine the nephrotoxic potential of putative DFPS metabolites and to determine if DFPS is metabolized differently from NDPS. Male Fischer-344 rats were administered (1.0 mmol/kg. i.p. in corn oil) DFPS, N-(3,5-difluorophenyl)succinamic acid (DFPSA), N-(3,5-difluorophenyl)-2-hydroxysuccinimide (DFHS), N-(3,5-difluorophenyl)-2- or -3-hydroxysuccinamic acids (2- and 3-DFHSA, respectively), N-(3,5-difluoro-4-hydroxyphenyl)succinimide (DFHPS). N-(3,5-difluoro-4-hydroxyphenyl) succinamic acid (DFHPSA) or corn oil only (1.2 ml/kg). Although some of the compounds produced changes in renal function and histology, these alterations were not indicative of irreversible kidney damage. DFPSA, 2-DFHSA, 3-DFHSA and DFHPSA were detected in the urine of rats 3 h after administration of 0.2 mmol/kg [14C]DFPS. The same metabolites were produced by isolated rat hepatocytes, but not by renal proximal tubule cells. Formation of the oxidative metabolites in vitro was prevented by the cytochrome P450 inhibitor 1-aminobenzotriazole. It appears that DFPS undergoes hepatic biotransformation similar to NDPS and that some of its metabolites have reversible effects on renal proximal tubules.

Nephrotoxicity of N-(3-bromophenyl)-2-hydroxysuccinimide: role of halogen groups in the nephrotoxic potential of N-(halophenyl) succinimides

Among N-(halophenyl)succinimides. N-(3,5-dichlorophenyl)succinimide (NDPS) is a potent nephrotoxicant as well as an agricultural fungicide. Although two chloride groups on the phenyl ring are essential to induce optimal nephrotoxicity, the role of halogen groups in NDPS nephrotoxicity is not clear. In this study, N-(3-bromophenyl)-2-hydroxysuccinimide (NBPHS) was prepared as a monohalophenyl derivative of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), an oxidative and nephrotoxicant metabolite of NDPS. The nephrotoxic potential of NBPHS was evaluated in vivo and in vitro to determine the role of halogen groups in N-(halophenyl)succinimide nephrotoxicity. Male Fischer 344 rats (four/group) were administered a single intraperitoneal (i.p.) injection of NBPHS (0.1, 0.4 or 0.8 mmol/kg) or vehicle (25% dimethyl sulfoxide in sesame oil) and renal function monitored for 48 h. Administration of NBPHS (0.8 mmol/kg) induced nephrotoxicity, while very mild changes or no changes in renal function were observed following administration of 0.4 mmol/kg or 0.1 mmol/kg of NBPHS, respectively. Nephrotoxicity induced by NBPHS (0.8 mmol/kg) was characterized by diuresis, transiently increased proteinuria, glucosuria and hematuria elevated kidney weight and reduced tetraethylammonium (TEA) uptake by renal cortical slices, and was not as marked as nephrotoxicity induced by NDHS (0.1 mmol/kg) or NDPS (0.4 mmol/kg). In the in vitro studies the effects of NBPHS on organic ion accumulation, pyruvate-stimulated gluconeogenesis, and lactate dehydrogenase (LDH) release were measured using renal cortical slices. NBPHS decreased p-aminohippurate (PAH) and TEA accumulation at NBPHS bath concentrations of 0.05 mM and 0.5 mM and 0.5 mM or greater, respectively. Renal gluconeogenesis was inhibited by NBPHS at 1 mM bath concentration, while LDH leakage was not increased at NBPHS bath concentrations up to 1 mM. The results demonstrate that NBPHS is a mild nephrotoxicant in vivo and in vitro, but does not have cytotoxic effects to renal tissues at the concentrations tested. From these results, it appears that halogen groups are essential to the nephrotoxic potential of N-(halophenyl)-2-hydroxysuccinimides or N-(halophenyl)succinimides and play an important role in the mechanism of NDPS nephrotoxicity following NDHS formation.

Role of chloride groups in the nephrotoxic potential of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide, an oxidative metabolite of N-(3,5-dichlorophenyl)succinimide

Although the addition of chloride groups to the phenyl ring of N-phenylsuccinimide (NPS) is known to enhance the nephrotoxic potential of NPS, the mechanism of this enhancement is unknown. One chlorinated NPS derivative, N-(3,5-dichlorophenyl)succinimide (NDPS), is a potent nephrotoxicant which induces marked proximal tubular necrosis at i.p. doses of 0.4 mmol/kg or greater. The purpose of this study was to compare the nephrotoxic potential of 2-hydroxy-N-phenylsuccinimide (HNPS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), an oxidative and nephrotoxicant metabolite of NDPS, to determine the importance of the chloride groups for the nephrotoxic potential of NDHS. Male Fischer 344 rats (4/group) were administered a single i.p. injection of HNPS (1.0 or 1.5 mmol/kg), NDHS (0.1 mmol/kg) or vehicle (25% dimethyl sulfoxide in sesame oil), and renal function measured at 24 and 48 h. HNPS was a nonnephrotoxicant at both doses tested, while NDHS induced marked nephrotoxicity characterized by diuresis, increased proteinuria, glucosuria, elevated blood urea nitrogen (BUN) concentration and kidney weight, decreased organic ion accumulation by renal cortical slices and proximal tubular necrosis. In vitro, HNPS reduced p-aminohippurate (PAH) and tetraethylammonium (TEA) accumulation beginning at HNPS bath concentrations of 0.05 and 0.5 mM, respectively. The results of this study indicate that although HNPS has direct effects on renal function in vitro, HNPS is not a nephrotoxicant in vivo at doses up to 15 times the minimal nephrotoxicant dose of NDHS. Therefore, the chloro groups present on NDHS play an essential role in the nephrotoxic potential of NDHS and contribute to aspects of the nephrotoxic mechanism of NDPS beyond NDPS oxidation to form NDHS.

Renal effects of N-(3,5-disubstitutedphenyl)-succinimides in the Fischer 344 rat

Previous studies have demonstrated the importance of substitution at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides for the production of nephrotoxicants in this series of compounds. The purpose of this study was to determine if the electronic nature of the 3,5-substituents is an important determinant for nephrotoxic potential. Male Fischer 344 rats (four rats per group) were administered a single intraperitoneal injection of a succinimide (0.4 or 1.0 mmol kg-1) or vehicle, and the renal function was monitored for 48 h. Only N-(3,5-dichlorophenyl)succinimide (0.4 or 1.0 mmol kg-1) induced marked changes in renal function. Urine volume, BUN concentration and proteinuria were increased following N-(3,5-dinitrophenyl)succinimide (1.0 mmol kg-1) treatment but other renal parameters and renal morphology were unchanged in this treatment group. These results indicate that the presence of halogen atoms at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides is more important for nephrotoxic potential than the presence of non-halogen substituents. The reason why halogen substitution is an important determinant for N-phenylsuccinimide nephrotoxicity is unknown.

Interactions among nephrotoxicants: N-(3,5-dichlorophenyl)succinimide and cephaloridine

Numerous studies have demonstrated the interactive potential between nephrotoxicants. The purpose of this study was to examine the interactive potential between two model nephrotoxicants, N-(3,5-dichlorophenyl)succinimide (NDPS) and cephaloridine (CPH). Male Fischer 344 rats (4 rats per group) were administered an intraperitoneal (i.p.) injection of CPH (500 mg/kg), NDPS (0.2 mmol/kg) or the appropriate vehicle 1 h prior to administration of an i.p. injection of NDPS (0.2, 0.4, or 1.0 mmol/kg), CPH (500, 750 or 1000 mg/kg) or the appropriate vehicle. Renal function was monitored at 24 and 48 h. Combination of non-nephrotoxic doses of CPH (500 mg/kg) and NDPS (0.2 mmol/kg) did not result in nephrotoxicity, regardless of which compound was administered first. NDPS (0.2 mmol/kg) weakly enhanced the nephrotoxicity observed following CPH (1000 mg/kg) injection but had little effect on CPH (750 mg/kg)-induced renal effects. However, CPH (500 mg/kg) markedly attenuated NDPS (0.4 or 1.0 mmol/kg)-induced nephrotoxicity. These results demonstrate that prior NDPS exposure has little effect on the outcome of CPH-induced renal effects, but prior CPH exposure can markedly alter the renal response to NDPS administration.

Toxicity of N-(3,5-dichlorophenyl)succinimide and metabolites to rat renal proximal tubules and mitochondria

The acute nephrotoxicity caused by N-(3,5-dichlorophenyl) succinimide (NDPS) has been shown to be due to a metabolite(s) of the parent compound. This study examined the toxicity of NDPS, its known metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA), N-(3,5-dichlorophenyl)malonamic acid (DMA), N-(3,5-dichlorophenyl)succinamic acid (NDPSA), and two postulated metabolites N-(3,5-dichlorophenyl)maleamic acid (NDPMA) and N-(3,5-dichlorophenyl)maleimide (NDPM) to suspensions of renal proximal tubules (RPT) prepared from male Fischer 344 rats. Tubule viability and mitochondrial function were not adversely affected by exposure of RPT to either 1 mM NDPS, NDHS, NDHSA, DMA, NDPSA, or NDPMA for 4 h. However, NDPM caused a concentration-(25-100 microM) and time-dependent (0.25-4 h) loss in basal and nystatin stimulated oxygen consumption and tubule viability. Investigations using isolated renal cortical mitochondria (RCM) showed that NDPM was a potent inhibitor of mitochondrial function. Isolated RCM respiring on pyruvate/malate and exposed to NDPM exhibited a concentration (25-100 microM) dependent decrease in state 3 and state 4 respiration. Inhibition of mitochondrial state 3 respiration by NDPM was mediated through site 1 of the respiratory chain. NDPM did not inhibit cytochrome c-cytochrome oxidase or the electron transport chain. These results indicated that NDPS, its known metabolites, and NDPMA were not directly toxic to rat RPT. However, the postulated metabolite NDPM, was a potent tubule cytotoxicant that inhibited mitochondrial function in isolated RCM and RPT and may produce cell death through this mechanism.

Acute nephrotoxicity induced by isomeric dichloroanilines in Fischer 344 rats

Chlorinated anilines are widely used as chemical intermediates in the manufacture of numerous dyes, pesticides, drugs and industrial compounds. The purpose of this study was to examine the nephrotoxic potential of the six dichloroaniline (DCA) isomers in vivo and in vitro. In the in vivo studies, male Fischer 344 rats (4-8 rats/group) were administered a single, intraperitoneal injection of a DCA isomer (0.4, 0.8 or 1.0 mmol/kg) as the hydrochloride salt or given vehicle (0.9% saline, 2.5 ml/kg), and renal function monitored at 24 and 48 h. Renal effects induced by DCA were characterized by decreased urine volume, increased proteinuria, hematuria, modest elevations in blood urea nitrogen (BUN) concentrations, decreased accumulation of p-aminohippurate (PAH) by renal cortical slices, and no change or a slight decrease in kidney weight. Renal morphological changes were observed as proximal tubular necrosis with lesser effects on distal tubular cells and collecting ducts. Based on the overall effects on renal function and morphology, the decreasing order of nephrotoxic potential was found to be 3,5-DCA greater than 2,5-DCA greater than 2,4-, 2,6- and 3,4-DCA greater than 2,3-DCA. The ability for the DCA to induce nephrotoxicity correlated well with the lipophilic properties of the DCA isomers and Hammett constants (sigma) for the various chloro substitutions. In the in vitro studies, renal cortical slices from naive male Fischer 344 rats were co-incubated with a DCA isomer (0-10(-3) M) and PAH or tetraethylammonium (TEA). All DCA isomers decreased PAH and TEA accumulation at 10(-3) M DCA concentration in the media with 3,5-DCA inducing the largest decrease at this concentration. These results indicate that DCA are capable of altering renal function in vivo and in vitro and that 3,5-DCA possesses the greatest nephrotoxic potential in vivo and in vitro.

Acute toxicity induced by 2-aryl-N-methylsuccinimides

Phensuximide (PSX) is a 2-arylsuccinimide useful in the treatment of absence seizures. PSX is a mild urotoxicant and is structurally related to N-phenylsuccinimide (NPS) and its antifungal derivatives. Since substitution of the phenyl ring of NPS with chloro or tert-butyl groups can produce compounds with enhanced nephrotoxic potential, it was felt that similar substitutions on the phenyl ring of PSX also might produce derivatives with enhanced nephrotoxic potential. Three derivatives of PSX were prepared and tested: 2-(3-chlorophenyl)-N-methylsuccinimide (CPMS); 2-(4-tert-butylphenyl)-N-methylsuccinimide (BPMS) and 2-(3,5-dichlorophenyl)-N-methylsuccinimide (DPMS). In one set of experiments, male Fischer 344 rats were administered a single intraperitoneal (i.p.) injection of a succinimide (0.4 or 1.0 mmol kg-1) or vehicle (sesame oil, 2.5 ml kg-1) and renal function monitored at 24 and 48 h. Only minor changes in renal function were noted with the PSX derivatives. BPMS and DPMS (1.0 mmol kg-1) treatment induced mild renal tubular necrosis and thickening of the glomerular membranes. However, no significant morphological changes were noted in ureters, bladder or liver in any treatment group. In a second set of experiments, rats were pretreated with phenobarbital (75 mg kg-1 day-1, i.p., 3 days) followed by a single i.p. injection of DPMS (0.4 or 1.0 mmol kg-1) or DPMS vehicle. Renal function was monitored as before. Phenobarbital pretreatment did not markedly enhance the functional nephrotoxicity induced by DPMS (0.4 mmol), but tubular necrosis was greater than observed in non-phenobarbital-pretreated rats receiving DPMS (1.0 mmol kg-1). In addition, hepatotoxicity was observed as the appearance of numerous non-staining vacuoles in hypertrophied hepatocytes. In the phenobarbital plus DPMS (1.0 mmol kg-1) treatment group, all rats died by 48 h. Prior to death, rats exhibited increased proteinuria (+3), hematuria (+3) and blood urea nitrogen concentration. At 24 h, kidneys from rats treated with phenobarbital plus DPMS (1.0 mmol kg-1) exhibited extensive proximal tubular necrosis and numerous glomeruli with thickened membranes. Hepatotoxicity was more pronounced than with phenobarbital plus DPMS (0.4 mmol kg-1) at 48 h and urinary bladders had focal areas of erythrocytes pooling below the epithelial lining. These results demonstrate that although NPS and PSX are structural analogs, chemical substitutions that enhance the nephrotoxic potential of NPS do not have a similar effect on PSX. In addition, DPMS can induce urotoxicity in a manner similar to that observed for PSX and probably induces toxicity via one or more metabolites.

Renal and hepatic toxicity of N-arylsuccinimides in Fischer 344 rats

The role of aromaticity in the nephrotoxic potential of N-arylsuccinimides was studied in male Fischer 344 rats. Rats were administered a single intraperitoneal (i.p.) injection of an N-arylsuccinimide derivative (0.4 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg), and the renal function monitored at 24 and 48 h. The parent compound in this series, N-phenylsuccinimide (NPS), had previously been shown to induce only minimal renal effects, having no effect on urine volume, blood urea nitrogen concentration, kidney weight, p-aminohippurate accumulation or renal morphology. Only an increase in tetraethylammonium uptake has been observed following NPS administration to rats. These effects were not enhanced by reducing aromaticity (N-cyclohexylsuccinimide (NCS]. Compounds with increased aromaticity N-(1-naphthyl)succinimide (NNS), N-(1-anthracenyl)succinimide (1-NAS) and N-(9-anthracenyl)succinimide (9-NAS)--also only weakly affected renal function. However, NNS (1.0 mmol/kg) and, to a lesser degree, 9-NAS (1.0 mmol/kg) proved to be hepatotoxins. Liver damage was most pronounced near central vein regions of the lobule and least evident around periportal sites. Damaged liver tissue exhibited unusually large deposits of connective tissue and hypertrophied hepatocytes with numerous vacuoles in their cytoplasm. Therefore, derivatives of NPS with increased or decreased aromaticity relative to the parent compound do not exhibit the ability to induce moderate or marked nephrotoxicity. However, increasing aromaticity did produce the derivatives NNS and 9-NAS, which are hepatotoxins. These compounds represent the first members in this series of compounds to induce acute hepatotoxicity.

Comparative acute renal effects of three N-(3,5-dichlorophenyl)carboximide fungicides: N-(3,5-dichlorophenyl)succinimide, vinclozolin and iprodione

A large number of carboximides have been synthesized, tested and, in some cases, marketed as agricultural fungicidal agents. One carboximide fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) proved to be both highly efficacious as a fungicide and a nephrotoxin. The purpose of this study was to compare the acute nephrotoxic potential of three N-(3,5-dichlorophenyl)carboximide fungicides [NDPS, vinclozolin (VCLZ) and iprodione (IPDO)] to determine if nephrotoxic potential correlated with fungicidal efficacy among this class of structurally-related agricultural agents. Male Fischer 344 rats (4 rats/group) received a single intraperitoneal injection of a fungicide (0.4 or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg), and renal function was monitored at 24 and 48 h. NDPS (0.4 or 1.0 mmol/kg)-induced renal effects were characterized by marked diuresis, increased proteinuria, elevated blood urea nitrogen (BUN) concentration and kidney weights, decreased organic ion accumulation by renal cortical slices and proximal tubular necrosis. In contrast, IPDO and VCLZ (0.4 or 1.0 mmol/kg) administration resulted in only minor or no alterations in the renal function parameters studied and renal morphology. These results suggest that fungicidal efficacy does not correlate with acute nephrotoxic potential among the N-(3,5-dichlorophenyl)carboximide fungicides.

Nephrotoxicity of N-(3,5-dichlorophenyl)succinimide metabolites in vivo and in vitro

The experimental fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) has been shown to produce selective nephrotoxicity at least in part through the actions of one or more metabolites. The purpose of this study was to (1) determine the nephrotoxic potential of three known NDPS metabolites; N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA), and N-(3,5-dichlorophenyl)malonamic acid (DMA) and (2) examine the role of renal biotransformation in NDPS-induced nephrotoxicity. In one set of experiments, male Fischer 344 rats were administered a single intraperitoneal (ip) injection of NDPS or a NDPS metabolite (0.2, 0.4, or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg) and renal function was monitored at 24 and 48 hr. Both NDHS and NDHSA administration (0.2 or 0.4 mmol/kg) resulted in nephrotoxicity similar to that produced by NDPS (0.4 or 1.0 mmol/kg). DMA administration resulted in only minor renal effects. Addition of NDPS to renal cortical slices prepared from naive Fischer 344 rats resulted in decreases in p-aminohippurate (PAH) and tetraethylammonium (TEA) accumulation at NDPS media concentrations of 10(-4) and 10(-5) M or greater, respectively. Pretreatment of rats with microsomal enzyme activity modifiers (phenobarbital, 3-methylcholanthrene, cobalt chloride, or piperonyl butoxide) had little effect on in vitro effects of NDPS on PAH or TEA accumulation. A pattern of PAH or TEA uptake similar to that observed for NDPS was observed in vitro with NDPS-d4, a nonnephrotoxic analog of NDPS labeled on the succinimide ring with deuterium. Of the NDPS metabolites tested in vitro for nephrotoxicity, only NDHS produced decreases in PAH and TEA accumulation similar to those produced by NDPS. These results suggest that the NDPS metabolites NDHS and NDHSA are nephrotoxic compounds. However, the role of these metabolites in NDPS-induced nephrotoxicity remains to be determined. In addition, it appears that NDPS has direct effects on renal function, but these effects do not appear to be of major toxicological significance in vivo. Direct renal bioactivation of NDPS or its known metabolites to nephrotoxic species does not appear to occur in vitro.

Effect of microsomal enzyme activity modulation on N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity

N-(3,5-Dichlorophenyl)succinimide (NDPS) is an experimental agricultural fungicide which has been shown to be a selective nephrotoxin. The purpose of this study was to determine if a NDPS metabolite contributes to acute NDPS-induced nephrotoxicity. Male Sprague-Dawley or Fischer 344 rats were pretreated with a microsomal enzyme inducer [phenobarbital (PB) or 3-methylcholanthrene (3-MC)] or inhibitor [cobalt chloride (CoCl2) or piperonyl butoxide (PIBX)] followed by a single intraperitoneal injection of NDPS (0.2, 0.4 or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg). Renal function was monitored at 24 and 48 h. CoCl2 or PIBX pretreatment reduced NDPS-induced diuresis, proteinuria and hematuria, and reduced the increases seen in the blood urea nitrogen (BUN) concentration and kidney weight. NDPS-induced decreases in organic ion accumulation were not markedly altered by CoCl2 or PIBX pretreatment. PB pretreatment enhanced all NDPS- (0.2 mmol/kg) induced renal effects, while 3-MC pretreatment protected against NDPS-induced diuresis, proteinuria, hematuria, and increases in the BUN concentration observed in both rat strains. Kidney weight and organic ion uptake changes were not substantially different between NDPS-treated rats with or without 3-MC pretreatment. It was concluded that a metabolite(s) contributes to or is responsible for acute NDPS-induced nephrotoxicity and that at least 1 toxic metabolite might be of extrarenal origin.

Role of glutathione in acute N-(3,5-dichlorophenyl) succinimide-induced nephrotoxicity in Sprague-Dawley and Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS), an experimental agricultural fungicide, has been shown to be a selective nephrotoxin in Sprague-Dawley and Fischer 344 rats. Previous studies have demonstrated that a toxic metabolite contributes to or is responsible for acute NDPS-induced nephrotoxicity. The purpose of this study was to investigate the role of glutathione in NDPS-induced renal effects. In 1 set of experiments, male Sprague-Dawley or Fischer 344 rats received a single intraperitoneal (i.p.) injection of NDPS (0.4 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg). Rats were killed at 1, 3, 6 or 24 h, and reduced (GSH) and oxidized (GSSG) glutathione concentrations determined in liver and renal cortex. In both rat strains NDPS (0.4 or 1.0 mmol/kg) administration produced small decreases in GSH concentrations (1 and 3 h) but moderate increases in GSSG concentrations (1 and 3 h) in liver and kidney. At 24 h both GSH and GSSG concentrations were increased, particularly in kidney. In a second set of experiments, rats were pretreated with the glutathione depletor diethyl maleate (DEM) (0.4 ml/kg, i.p.) 1 h prior to NDPS (0.2, 0.4 or 1.0 mmol/kg, i.p.) or sesame oil (2.5 ml/kg, i.p.) administration, and renal function monitored at 24 and 48 h. DEM pretreatment attenuated the increase in urine volume (24 and 48 h), proteinuria, glucosuria, hematuria and elevated blood urea nitrogen (BUN) concentration produced by NDPS (0.4 or 1.0 mmol/kg) in both Sprague-Dawley and Fischer 344 rats. NDPS-induced increases in kidney weight also were generally prevented by DEM pretreatment. Proximal tubular necrosis produced by NDPS administration was reduced by DEM but not prevented. Pretreatment with the cysteine conjugate beta-lyase inhibitor amino-oxyacetic acid (0.5 mmol/kg, i.p.) 1 h prior to NDPS (0.4 or 1.0 mmol/kg) markedly attenuated all NDPS-induced effects on renal function and morphology. These results suggest that glutathione does not play a protective role against NDPS-induced renal effects and that a glutathione or cysteine conjugate of NDPS might contribute to NDPS-induced nephrotoxicity.

Structure-nephrotoxicity relationships for meta-substituted N-phenylsuccinimides

The N-phenylsuccinimides are being evaluated as experimental agricultural fungicides. The purpose of this study was to examine the relationship between the electron withdrawing or electron donating properties of phenyl ring substituents on meta-substituted N-phenylsuccinimide (NPS) derivatives and the nephrotoxic potential of the corresponding fungicides. Male Fischer 344 rats were administered a single intraperitoneal injection of a succinimide (0.4 or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg), and renal function monitored at 24 and 48 hr. Non-halogen-substituted NPS derivatives produced little evidence of nephrotoxicity at the doses used in this study. Among the meta-halogen derivatives of NPS, N-(3-chlorophenyl)succinimide (NCPS) was the most nephrotoxic. NCPS-induced nephrotoxicity was characterized by diuresis, proteinuria, hematuria, elevated blood urea nitrogen (BUN) concentration, decreased organic ion accumulation and proximal tubular necrosis. However, all renal effects produced by NCPS were mild to moderate. These results suggest that the electron withdrawing or donating property of a functional group is not a good predictor of the nephrotoxic potential for the corresponding fungicide. In addition, lipophilicity did not correlate with nephrotoxic potential for the meta-substituted NPS derivatives evaluated in this study.

Nephrotoxicity of N-(3,5-dihalophenyl)succinimides in Fischer 344 rats

Previous studies have demonstrated that N-(3,5-dichlorophenyl)succinimide (NDCPS) is the most nephrotoxic compound among the N-(mono- or dichlorophenyl)succinimides. The purpose of this study was to examine the nephrotoxic potential of the different N-(3,5-dihalophenyl)succinimides (NDHPS) to determine the importance of the halogen species for NDHPS-induced nephrotoxicity. Male Fischer 344 rats were administered a single intraperitoneal injection of an NDHPS (0.4, 0.8, or 1.0 mmol/kg) or vehicle (2.5 ml/kg), and renal function was monitored at 24 and 48 h. NDCPS or N-(3,5-diiodophenyl)succinimide administration produced the greatest nephrotoxic response. Nephrotoxicity was characterized by diuresis, increased proteinuria, glucosuria, increased kidney weight and blood urea nitrogen (BUN) concentration, decreased accumulation of p-aminohippurate (PAH) and tetraethylammonium (TEA) by renal cortical slices and proximal tubular necrosis. N-(3,5-Dibromophenyl)succinimide injection produced mild nephrotoxicity, while N-(3,5,-difluorophenyl)succinimide administration did not result in nephrotoxicity. These results indicate that the halogen species can influence the nephrotoxicity produced by the NDHPS. In addition, nephrotoxic potential did not correlate with fungicidal efficacy, which suggests that the nephrotoxic and fungicidal mechanisms of these compounds might be different.

Deuterium isotope effect in acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity

Deuterium labelling of the succinimide ring of N-(3,5-dichlorophenyl) succinimide (NDPS) markedly reduced the acute nephrotoxicity produced by NDPS administration to Fischer 344 rats. Administration of the deuterium-labelled derivative, NDPS-d4, to male Fischer 344 rats failed to produce the marked diuresis, increased proteinuria, glucosuria, hematuria, elevated blood urea nitrogen (BUN) concentration and kidney weight, decreased basal p-aminohippurate (PAH) accumulation, and proximal tubular necrosis which are characteristic of NDPS-induced nephrotoxicity. However, lactate-stimulated PAH and tetraethylammonium (TEA) accumulation were decreased by NDPS-d4 (1.0 mmol/kg). The lack of nephrotoxicity produced by NDPS-d4 suggests that oxidation at the carbon-carbon bridge of the succinimide ring is an important biotransformation step in the generation of the nephrotoxic species of NDPS.

In vivo and in vitro nephrotoxicity of aniline and its monochlorophenyl derivatives in the Fischer 344 rat

Aniline (A) and its monochlorophenyl derivatives (2-CA, 3-CA and 4-CA) are widely-used chemical intermediates. In the present study, the in vivo and in vitro nephrotoxic potential of these compounds was assessed in Fischer 344 rats. In the in vivo experiments, rats were administered a single intraperitoneal (i.p.) injection of an aniline (0.4, 1.0 or 1.5 mmol/kg) or 0.9% saline (2.0 ml/kg, i.p.), and renal function monitored at 24 and 48 h. 2-CA was the only compound tested which decreased urine volume, elevated the blood urea nitrogen (BUN) concentration and depressed both basal and lactatestimulated p-aminohippurate (PAH) accumulation by renal cortical slices at the 1.0 mmol/ kg dose. Similar results were produced following 3- and 4-CA administration, but these compounds required a dose of 1.5 mmol/kg. Aniline had little effect on renal function at the doses used in this study. In the in vitro experiments, 2-CA (10(-4) M or greater) depressed basal PAH accumulation. Tetraethylammonium (TEA) uptake was decreased by all compounds with an incubate concentration of the aniline at 10(-3) M. Lactatestimulated PAH uptake was not decreased by any test compound. These results indicate that chlorine substitution on the phenyl ring of aniline enhances nephrotoxic potential, and that 2-substitution produces the greatest increase.

3,5-Dichloroaniline-induced nephrotoxicity in the Sprague-Dawley rat

The nephrotoxic potential of 3,5-dichloroaniline (DCA) was examined in male Sprague-Dawley rats. Rats were administered DCA (0.4, 0.8 or 1.0 mmol/kg, i.p.), or 0.9% saline (1.0 ml/kg, i.p.), and renal function was monitored at 24 and 48 h. DCA (0.4 mmol/kg) administration did not produce evidence of nephrotoxicity. However, DCA (0.8 mmol/kg) administration decreased urine volume and osmolality, increased proteinuria, elevated the blood urea nitrogen (BUN) concentration and decreased basal and lactate-stimulated p-aminohippurate (PAH) accumulation. Three of 4 rats receiving DCA (1.0 mmol/kg) died prior to 48 h postinjection. Incubation of renal cortical slices with DCA resulted in decreased PAH and tetraethylammonium (TEA) uptake when DCA concentrations of 10(-6) M or greater were used. These results indicate that DCA is nephrotoxic to Sprague-Dawley rats when administered in a dose of 0.8 mmol/kg or higher and is capable of altering organic ion transport in vitro.

Effect of succinimide ring modification on N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Sprague-Dawley and Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) has proven to be an effective experimental agricultural fungicide. However, NDPS produces marked nephrotoxicity in Sprague-Dawley and Fischer 344 rats. The purpose of this study was to determine the importance of an intact, unsubstituted succinimide ring for acute NDPS-induced nephrotoxicity. Structural modifications included ring opening, reduction of one or both carbonyl groups, breaking the ethylene carbon-carbon bond and mono- or dialkyl substitution on the succinimide ring. Sprague-Dawley or Fischer 344 rats were administered NDPS or an NDPS analog (0.1, 0.2, 0.4, 0.8 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg, i.p.) and renal function was monitored at 24 h and 48 h. All structural modifications produced compounds with markedly reduced nephrotoxic potential in both Sprague-Dawley and Fischer 344 rats when compared to NDPS. However, N,N-diacetyl-3,5-dichloroaniline and N-(3,5-dichlorophenyl)pyrrolidine-2-one were more lethal than NDPS. The reduced renal effects of the NDPS analogs did not correlate with lipophilic character. These results indicate that an intact, unsubstituted succinimide ring is optimal for acute NDPS-induced nephrotoxicity.

Structure-nephrotoxicity relationships for para-substituted N-phenylsuccinimides in Sprague-Dawley and Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) has proven to be one of the most nephrotoxic compounds of a series of N-(halophenyl)succinimides. Previous studies in our laboratory have demonstrated that chlorine content and position on the phenyl ring are important determinants for NDPS-induced nephrotoxicity. The purpose of this study was to investigate the relationship between the electron donating or withdrawing nature of phenyl group substituents and the nephrotoxic potential of the corresponding fungicides. Rats were administered a para-substituted N-phenylsuccinimide (0.4 or 1.0 mmol/kg, i.p.) or sesame oil (2.5 ml/kg, i.p.), and renal function was monitored at 24 h and 48 h. In Sprague-Dawley rats, a clear nephrotoxicity was produced by NDPS. Weak nephrotoxicity was produced by N-(4-tert-butylphenyl)succinimide (NBPS). NDPS also was the most nephrotoxic compound in Fischer 344 rats, while weak nephrotoxicity was produced by NBPS. Lipophilic character (e.g. partition coefficient) did not correlate with acute nephrotoxicity in either rat strain. These results also indicate that there is a no correlation between the electronic nature of the phenyl substituents and resulting nephrotoxicity.