Sodium sulfate potentiates N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity in the Fischer 344 rat

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity as its major toxicity in rats. Previous studies have shown that NDPS induces nephrotoxicity following oxidation of the succinimide ring to form N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and the hydrolysis product of NDHS, N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). Our recent work found that sodium sulfate potentiated NDPS nephrotoxicity, suggesting that sulfate conjugation of NDPS metabolites might be a bioactivation step mediating NDPS nephrotoxicity. The purpose of this study was to determine if sodium sulfate also potentiated the nephrotoxicity of the two nephrotoxic metabolites of NDPS and further to see if sodium sulfate potentiated NDHS and 2-NDHSA nephrotoxicity to the same degree. Male Fischer 344 rats (4-16 rats/group) received an intraperitoneal (ip) injection of sodium sulfate (10 mg/kg) 20 min before a non-nephrotoxic dose (0.05 mmol/kg, ip) of NDHS or 2-NDHSA, or vehicle (12.5% dimethyl sulfoxide in sesame oil). Renal function was then monitored over 48 h. Sodium sulfate pretreatment potentiated the renal effects of a non-nephrotoxic dose of NDHS and 2-NDHSA to induce nephrotoxicity. Nephrotoxicity was characterized by diuresis, increased proteinuria, elevated blood urea nitrogen (BUN) concentration, increased kidney weight and proximal tubular necrosis. Differences in the potentiation of NDHS and 2-NDHSA nephrotoxicity by sodium sulfate were also observed as NDHS nephrotoxicity was potentiated to a lesser degree than 2-NDHSA-induced nephrotoxicity. These results support the likelihood that one or more sulfate conjugate(s) of NDPS metabolites contribute to NDPS nephrotoxicity.     

Effect of buthionine sulfoximine on acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Fischer 344 rats

The experimental agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) has been shown to be a nephrotoxicant in Fischer 344 rats. Results of a previous study conducted in our laboratory suggested that glutathione might be an important modulator of NDPS-induced nephrotoxicity. The purpose of this study was to examine the effect of DL-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione synthesis, on NDPS-induced renal effects. Male Fischer 344 rats received an intraperitoneal (i.p.) injection of BSO (890 mg/kg) in 0.9% saline (10 ml/kg) followed 2 h later by an i.p. injection of NDPS (0.4 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg), and renal function monitored at 24 and 48 h. BSO pretreatment attenuated the diuresis, proteinuria, elevation in blood urea nitrogen (BUN) concentration and kidney weight, and decreases in organic ion accumulation by renal cortical slices induced by NDPS (0.4 or 1.0 mmol/kg) administration. Proximal tubular necrosis induced by NDPS administration also was attenuated by BSO pretreatment. These results indicate that BSO pretreatment attenuates NDPS-induced renal effects and that glutathione is important for modulating acute NDPS-induced nephropathy.     

Role of stereochemistry in N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity.

The nephrotoxicity induced by the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is mediated through oxidative metabolites of NDPS. Oxidation of the succinimide ring in NDPS yields the nephrotoxic metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and its hydrolysis product N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). The oxidation of NDPS on the succinimide ring also introduces an asymmetric carbon atom into these NDPS metabolites, so that R- and S- enantiomers of NDHS and 2-NDHSA are possible. The purpose of this study was to begin to explore the importance of the stereochemical orientation at the asymmetric carbon atom for the nephrotoxicity induced by NDPS metabolites. Male Fischer 344 rats were administered a single intraperitoneal (ip) injection of R-(+)- or S-(-)-2-NDHSA (0.05, 0.1 or 2.0 mmol/kg) or vehicle, and renal function was monitored for 48 h. R-2-NDHSA (0.1 mmol/kg) administration had little effect on renal function. R-2-NDHSA (0.2 mmol/kg) treatment induced mild diuresis on day 1, increased proteinuria, and a small increase in blood urea nitrogen (BUN) concentration, but no change in kidney weight or glucosuria. S-2-NDHSA (0.1 mmol/kg) induced marked nephrotoxicity as evidenced by diuresis on both post-treatment days, increased proteinuria, glucosuria, and increased kidney weight and BUN concentration. No evidence of hepatotoxicity was obtained in any treated group. Thus, the S-isomer of 2-NDHSA is a more potent nephrotoxicant than the R-isomer, and stereochemistry may play a role in NDPS metabolite-induced nephrotoxicity.     

Acute nephrotoxicity induced by N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid in Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) induces nephrotoxicity via one or more metabolites which arise from oxidation of the succinimide ring. The purpose of this study was to examine the nephrotoxic potential of N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid (3-NDHSA), a potential metabolite of NDPS and a positional isomer of N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA), a known nephrotoxic metabolite of NDPS. Male Fischer 344 rats were administered a single intraperitoneal injection of 3-NDHSA (0.2 or 0.4 mmol/kg) or sesame oil (2.5 mmol/kg), and renal function was monitored at 24 and 48 h. Both doses of 3-NDHSA induced diuresis, increased proteinuria, glucosuria and hematuria, elevated blood urea nitrogen (BUN) concentrations and kidney weights, decreased organic ion accumulation by renal cortical slices, and induced proximal tubular necrosis. The characteristics of 3-NDHSA-induced nephrotoxicity were identical to NDPS-induced nephropathy, but were evident at lower doses with 3-NDHSA. These results demonstrate that 3-NDHSA is a nephrotoxicant which might contribute to NDPS-induced nephropathy.     

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 a 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 ?M, 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 NDHS and contribute to aspects of the nephrotoxic mechanism of NDPS beyond NDPS oxidation to form NDHS.     

Acetone effects on N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity

Acetone has been shown to potentiate the toxicity of many halogenated hydrocarbons. The purpose of this study was to determine if acetone could alter the acute nephrotoxicity produced by the experimental fungicide N-(3,5-dichlorophenyl)succinimide (NDPS). Male Fischer 344 rats were administered acetone (1, 5 or 10 mmol/kg) or acetone vehicle (corn oil, 10 mg/kg) orally followed 16 h later by a single intraperitoneal injection of NDPS (0.2 or 0.4 mmol/kg) or NDPS vehicle (sesame oil, 2.5 ml/kg) and renal function was monitored at 24 and 48 h. Acetone (1 or 5 mmol/kg) did not alter NDPS (0.2 mmol/kg)-induced renal effects while acetone (10 mmol/kg) pretreatment attenuated NDPS (0.4 mmol/kg)-induced increases in blood urea nitrogen (BUN) concentration and kidney weight but had no effect on NDPS (0.4 mol/kg)-induced changes in urine volume or content, organic ion accumulation by renal cortical slices or renal morphology. These results suggest that acetone weakly attenuates NDPS-induced nephrotoxicity.     

Nephrotoxicity induced by N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid in male and female Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is a more potent nephrotoxicant in female rats than in males. Similarly, nephrotoxicant NDPS metabolites studied to date in male and female rats have also demonstrated gender differences, being twice as potent as nephrotoxicants in females as in males. The purpose of this study was to examine the nephrotoxic potential of N-(3,5-dichlorophenyl)-3-hydroxysuccinimide (3-NDHSA) in male and female Fisher 344 rats to determine if gender differences in nephrotoxic potential also exist for this metabolite. Rats (four per group) were administered a single intraperitoneal (i.p.) injection of 3-NDHSA (0.1, 0.2 or 0.4 mmol kg(-1)) or vehicle, and renal function was monitored at 24 and 48 h. 3-NDHSA 0.1 mmol kg(-1) did not induce nephrotoxicity in male or female rats. In male rats, 3-NDHSA 0.2 mmol kg(-1) induced mild nephrotoxicity seen as diuresis and transient, mild proteinuria. However, 3-NDHSA 0.4 mmol kg(-1) induced marked nephrotoxicity. In female rats, 3-NDHSA 0.2 mmol kg(-1) induced mild nephrotoxicity, as evidenced by transient diuresis and proteinuria. As in males, 3-NDHSA 0.4 mmol kg(-1) induced marked nephrotoxicity. These results indicate that, unlike NDPS and other nephrotoxic NDPS metabolites, 3-NDHSA does not exhibit gender differences in nephrotoxic potential. In addition, in comparison with NDPS and other nephrotoxic NDPS metabolites, 3-NDHSA is a less potent nephrotoxicant that NDHS or 2-NDHSA and similar to NDPS in nephrotoxic potential in male rats.     

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.     

N-(3,5-dichlorophenyl)succinimide nephrotoxicity in streptozotocin-induced diabetic rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) is an experimental fungicide which induces renal toxicity. The following study examined the nephrotoxicity induced by NDPS in streptozotocin (STZ) diabetic rats. Male Fischer 344 (F344) rats were injected with 35 mg/kg STZ (i.p.) or citrate buffer. Fourteen days after STZ or citrate buffer injection, the rats (4-6 rats/group) were injected with (0.4 or 1.0 mmol/kg) NDPS or vehicle (sesame oil, 2.5 ml/kg). Kidney weight, blood urea nitrogen (BUN) levels, morphology and renal cortical slice uptake of organic ions was quantitated 48 h after NDPS administration. A 0.4 mmol/kg dose of NDPS induced diuresis, increased kidney weight and a moderate elevation in BUN levels in the normoglycemic group. The 1.0 mmol/kg dose of NDPS produced diuresis, proteinuria, increased kidney weight and a marked increase in BUN levels in the normoglycemic group. The renal cortical slice uptake of p-aminohippurate (PAH) and tetraethylammonium (TEA) was also decreased 48 h after NDPS injection in the normoglycemic group. No alterations in kidney weight, BUN levels, morphology or renal cortical slice uptake of organic ions was observed in the diabetic animals treated with (0.4 or 1.0 mmol/kg) NDPS. The results of this study indicate that the renal toxicity of NDPS was reduced in the diabetic rat.     

Effect of autacoid modulation on N-(3,5-dichlorophenyl)succinimide (NDPS) and NDPS metabolite nephrotoxicity.

N-(3,5-Dichlorophenyl)succinimide (NDPS) is an agricultural fungicide which has been shown to induce acute tubular necrosis. The purpose of the present study was to determine if creatinine clearance was altered early in the development of NDPS nephrotoxicity. This study also examined the effect of autacoid modulation on the renal effects induced by NDPS and two metabolites of NDPS, N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA). In one set of experiments, male Fischer 344 rats (4 rats/group) were administered a single intraperitoneal (i.p.) injection of NDPS (1.0 mmol/kg) or vehicle and creatinine clearance was determined at 3 and 6 h post-treatment. NDPS administration resulted in a marked decrease in creatinine clearance at both time points. In a second set of experiments, rats (4–8 rats/group) were pretreated with the cyclooxygenase inhibitor indomethacin (3.0 or 5.0 mg/kg, i.p.) or the thromboxane synthase inhibitor dazmegrel (20 mg/kg, i.p.) 1 h before the i.p. administration of NDPS (0.2 or 0.4 mmol/kg), NDHS (0.05 or 0.1 mmol/kg), NDHSA (0.05 or 0.1 mmol/kg) or vehicle. Indomethacin pretreatment potentiated the nephrotoxic potential of NDPS and its two metabolites, while dazmegrel pretreatment attenuated NDPS nephrotoxicity without marked effects on NDHS or NDHSA nephropathy. These results indicate that renal hemodynamic changes occur early in the development of NDPS nephrotoxicity and that autacoids are important modulators of NDPS- and NDPS metabolite-induced renal effects.     

Effect of glucuronidation substrates/inhibitors on N-(3,5-dichlorophenyl)succinimide nephrotoxicity in Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is an acute nephrotoxicant in rats. Our previous studies have strongly suggested that glucuronide conjugation of NDPS metabolites might be a bioactivation step mediating NDPS nephrotoxicity. In this study, effects of substrates and/or inhibitors of primarily glucuronidation on NDPS nephrotoxicity were examined to explore further the role of glucuronidation in NDPS nephrotoxicity. Male Fischer 344 rats (4-6/group) were administered one of the following intraperitoneal (i.p.) pretreatments (dose, pretreatment time) prior to NDPS (0.4 mmol/kg) or NDPS vehicle (sesame oil, 2.5 ml/kg): (1) no pretreatment; (2) borneol (900 mg/kg, 30 min); (3) eugenol (500 mg/kg per day, 3 days); (4) clofibric acid (400 mg/kg, 15 min before (1/2 dose) and 3 h after (1/2 dose)), or (5) valproic acid, sodium salt (1.0 mmol/kg, 15 min). Following NDPS or NDPS vehicle administration, renal function was monitored at 24 and 48 h. Pretreatment with borneol or eugenol, substrates for ether glucuronidation and sulfation (mainly glucuronidation), afforded complete protection against NDPS nephrotoxicity. Substrates for acyl glucuronidation, clofibric acid or valproic acid, mildly reduced or had little effect on NDPS nephrotoxicity, respectively. These results suggest that ether glucuronide conjugates of NDPS metabolites, rather than acyl glucuronide conjugates, may be the primary ultimate nephrotoxicant species mediating NDPS nephrotoxicity.     

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.     

Nephrotoxicity induced by the R- and S-enantiomers of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and their sulfate conjugates in male Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity characterized as polyuric renal failure and mediated via metabolites arising from oxidation of the succinimide ring. Recent findings have suggested that the stereochemical nature of NDPS metabolites may be an important factor in NDPS metabolite-induced nephrotoxicity. The purpose of the present study was to determine the role of stereochemistry in the in vivo nephrotoxicity induced by R-(+)- and S-(-)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (R- and S-NDHS) and the in vitro nephrotoxicity induced by their enantiomeric sulfate conjugates, R-(-)- and S-(+)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide-O-sulfate (R- and S-NSC). Male Fischer 344 rats (four rats/group) were administered intraperitoneally (i.p.) an enantiomer of NDHS (0.05, 0.1 or 0.2 mmol/kg) or vehicle, and renal function monitored for 48 h. R-NDHS (0.1 or 0.2 mmol/kg) had little effect on renal function. In contrast, S-NDHS (0.1 mmol/kg) induced marked nephrotoxicity. The nephrotoxic potential of R- and S-NSC (0.5, 0.75 or 1.0mM) was determined using freshly isolated rat renal cortical cells (IRCC, 3-4 x 10(6)cells/ml). Cytotoxicity was determined by measuring the release of lactate dehydrogenase (LDH) at the end of a 1h incubation period. The LDH release observed in these studies was similar between R- and S-NSC. These results indicate that stereochemistry is an important factor for NDPS metabolite nephrotoxicity and that the role of stereochemistry, at least for NSC, occurs at extra-renal sites.     

Onset of and recovery from acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Sprague-Dawley rats

The time course for the onset of N-(3,5-dichlorophenyl)succinimide (NDPS)-induced nephrotoxicity was studied in male Sprague-Dawley rats. The ability of rats to recover from a single nephrotoxic dose (100 or 200 mg/kg) of NDPS also was examined. One hour following NDPS administration (200 mg/kg, i.p.), p-aminohippurate (PAH) accumulation by renal cortical slices was decreased 51%. Changes in renal morphology, proteinuria, hematuria, and diuresis were observed at 3 h. Renal damage at 6 h was similar to that seen at 24 h with tubular necrosis greater than that observed at 3 h and some lumina plugged with PAS+ material. Accumulation of both PAH and tetraethylammonium (TEA) by renal cortical slices was decreased; and proteinuria, hematuria, and polyuria were increased at 6 h and 24 h. Blood urea nitrogen (BUN) was not increased until 24 h. Renal function began to return to normal in rats receiving NDPS (100 mg/kg, i.p.) by 48 h, and functional recovery was complete by 168 h, although slight morphological changes were still evident. However, not all rats receiving NDPS (200 mg/kg, i.p.) recovered by 168 h, and some rats (3 of 7) died of renal failure between 96 h and 168 h. Widespread tubular necrosis and increased kidney weight were also present in this group at 168 h. Thus, NDPS-induced nephrotoxicity was evident by 1 h, established by 6 h and maximum between 24 h and 48 h. Recovery from NDPS-induced nephropathy was found to be dose-dependent, and incomplete in some animals at a dose of 200 mg/kg.     

Effect of three n-acetylamino acids on N-(3,5-dichlorophenyl)succinimide (NDPS) and ndps metabolite nephrotoxicity in Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity in mammals characterized as polyuric renal failure and proximal tubular necrosis. Recent studies have suggested that NDPS-induced nephrotoxicity may be mediated by metabolites arising from the nephrotoxic NDPS metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and/or N-(3,5-dichlorophenyl)-2-succinamic acid (2-NDHSA). The purpose of this study was to examine the effects of N-acetylcysteine (NAC), a nucleophilic agent, and two nonnucleophilic N-acetylamino acids, N-acetylserine (NAS) and N-acetylalanine (NAA), on NDPS and NDPS metabolite-induced nephrotoxicity. Male Fischer 344 rats (4-8/group) were administered intraperitoneally (ip) an N-acetylamino acid (1 mmol/kg) 2 h before an ip injection of NDPS (0.4 mmol/kg), NDHS (0.1 mmol/kg), 2-NDHSA (0.1 mmol/kg), or vehicle. Renal function was then monitored at 24 and 48 h. NAC pretreatment markedly attenuated NDPS-, NDHS-, and 2-NDHSA-mediated nephrotoxicity. The nonnucleophilic N-acetylamino acids (NAS, NAA) only partly reduced NDPS and NDHS nephrotoxicity, and they had little effect on 2-NDHSA nephrotoxicity. These results suggest that reactive NDPS metabolites may be formed from NDHS and 2-NDHSA and that nucleophilic substrates (e.g., NAC) may offer protection from NDPS-induced nephrotoxicity. However, mechanisms other than chemical neutralization of reactive NDPS metabolites may also be contributing to the attenuation of NDPS nephrotoxicity, since nonnucleophilic N-acetylamino acids (e.g., NAA) also provided some protection against NDPS and NDHS nephrotoxicity.     

Effect of calcium antagonism by nifedipine and chlorpromazine on acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Fischer 344 rats

The nephrotoxicity induced by a wide variety of chemical compounds can be attenuated by agents which modify calcium ion (Ca2+) movement across membranes or calcium-dependent processes. The purpose of this study was to examine the ability of nifedipine, a calcium channel blocking drug, and chlorpromazine (CPZ), an antagonist of many calcium-dependent processes, to attenuate the nephrotoxicity induced by the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) or its metabolite N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS). Male Fischer 344 rats (4 rats per group) were pretreated intraperitoneally (i.p.) with nifedipine (0.25 or 0.50 mg/kg), CPZ (1.0 or 5.0 mg/kg) or vehicle 1 h before NDPS (0.4 mmol/kg), NDHS (0.1 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg). In separate experiments, rats were pretreated with nifedipine (0.25 or 0.50 mg/kg/day, i.p.) starting 2 days before NDPS or NDPS vehicle and continuing throughout the experiment. Renal function was monitored at 24 and 48 h. Nifedipine (single or multiple treatments) and CPZ (1.0 mg/kg) were ineffective in substantially altering NDPS (0.4 mmol/kg)-induced nephrotoxicity. However, CPZ (5.0 mg/kg) markedly attenuated all aspects of NDPS-induced nephropathy. Also, CPZ (5.0 mg/kg) partially protected against NDHS (0.1 mmol/kg)-induced renal effects. These results demonstrate the inability of the calcium channel blocker nifedipine to attenuate NDPS nephrotoxicity. Attenuation of NDPS nephrotoxicity by CPZ could suggest that CPZ is antagonizing calcium influx into renal tissue and/or renal intracellular calcium-dependent processes to modify the renal response to NDPS. However, the inability of CPZ to markedly attenuate NDHS nephrotoxicity could indicate that CPZ protected against NDPS nephrotoxicity by inhibiting biotransformation of the parent compound to its toxic chemical species.     

Gender differences in the potentiation of N-(3,5-dichlorophenyl)succinimide metabolite nephrotoxicity by phenobarbital

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces acute nephrotoxicity characterized as polyuric renal failure with proximal tubular necrosis. Phenobarbital pretreatment potentiates NDPS and N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS, a nephrotoxic metabolite of NDPS) nephrotoxicity in male rats. The purpose of this study was to determine the ability of phenobarbital pretreatment to potentiate (1) NDHS nephrotoxicity in female rats and (2) N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA, a nephrotoxic metabolite of NDHS) nephrotoxicity in male and female rats. Age-matched male and female Fischer 344 rats (4/group) were pretreated intraperitoneally (ip) with phenobarbital (75 mg/d, 3 d). At 24 h after the last injection of phenobarbital, an ip injection of NDHS (0.025 mmol/kg), 2-NDHSA (0.025 mmol/kg, females; 0.05 mmol/kg, males), or vehicle was given and renal function was monitored at 24 and 48 h post NDPS metabolite or vehicle. Additional groups received the NDPS metabolite or vehicle only and were also monitored for 48 h. In a separate experiment, male Fischer 344 rats were pretreated with piperonyl butoxide (PIBX, 1360 mg/kg) or the PIBX vehicle. 2-NDHSA (0.1 mmol/kg) or vehicle was administered (ip) 30 min after PIBX, and renal function was monitored for 24 h. Phenobarbital markedly potentiated 2-NDHSA nephrotoxicity in male rats as evidenced by increased kidney weight, increased blood urea nitrogen (BUN) concentration, and decreased tetraethylammonium (TEA) accumulation by renal cortical slices. PIBX had no effect on 2-NDHSA nephrotoxicity. Phenobarbital pretreatment did not markedly enhance the nephrotoxic potential of NDHS or 2-NDHSA in female rats. These results indicate that phenobarbital exhibits differential potentiation of NDPS metabolite nephrotoxicity in male and female rats and that the potentiation of 2-NDHSA nephrotoxicity observed in males is not due to cytochrome P-450-mediated oxidative biotransformation.     

The effect of probenecid on acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in the Fischer 344 rat

N-(3,5-Dichlorophenyl)succinimide (NDPS), an experimental agricultural fungicide, has been shown to produce selective nephrotoxicity in rats. Previous studies have shown that a metabolite(s) of extrarenal origin contributes to acute NDPS-induced nephrotoxicity. The purpose of this study was to determine if the organic acid transport inhibitor probenecid could modify the renal toxicity produced by NDPS administration. Male Fischer 344 rats were administered a single intraperitoneal (i.p.) injection of probenecid (60, 90 and 120 mg/kg) or 0.9% saline (1.0 ml/kg) followed 30 min later by NDPS (0.4 or 1.0 mmol/kg, i.p.) or sesame oil (2.5 ml/kg, i.p.) Renal function was monitored at 24 h and 48 h. Probenecid (60 mg/kg) did not markedly alter NDPS-induced renal effects on either post-treatment day. However, pretreatment with probenecid (90 or 120 mg/kg) blocked or attenuated the diuresis, increased proteinuria, decreased tetraethylammonium (TEA), uptake, elevation in blood urea nitrogen (BUN) concentration and increased kidney weight produced by NDPS (0.4 mmol/kg) administration. Only increased kidney weight and BUN concentration, and decreased lactate-stimulated p-aminohippurate (PAH) uptake were altered by probenecid (120 mg/kg) pretreatment when NDPS (1.0 mmol/kg) was given. NDPS-induced changes in renal morphology were not prevented by pretreatment with any probenecid dose. These results suggest that at least one nephrotoxic metabolite of NDPS is an organic acid. However, this acidic metabolite might not be the major nephrotoxic metabolite or a precursor to the major nephrotoxic metabolite(s). The identity of these metabolites remains to be determined.     

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.