Dianne K. Anestis

Comparison of the in vitro toxicity of dichloroaniline structural isomers

Acute exposure to certain dichloroaniline (DCA) isomers results in renal and hepatic toxicity in vivo. In the present study we examined whether dichloroaniline structural isomers were cytotoxic to liver and kidney slices in vitro and compared the toxicities of the different structural isomers. These studies were necessary in order to validate the use of an in vitro slice system for examination of the cellular mechanisms for toxicity. Renal cortical and hepatic slices were incubated for 90 min with 2,3-DCA, 2,4-DCA, 2,5-DCA, 2,6-DCA, 3,4-DCA or 3,5-DCA at a final concentration of 0-1 mm. Pyruvate-directed gluconeogenesis was measured following an additional 30-min incubation with 10 mM pyruvate. Cytotoxicity was also determined by measurement of lactate dehydrogenase (LDH) release 120 min after the addition of dichloroaniline isomers at a final concentration of 0, 0.5, 1 or 2 mM. Gluconeogenesis in renal cortical slices was inhibited by all of the isomers beginning at a concentration of 0.5 mM. Renal slice LDH leakage was elevated above control levels by 1-2 mM 3,4-DCA or 3,5-DCA. A final concentration of 2 mM was needed for 2,3-DCA, 2,4-DCA, 2,5-DCA or 2,6-DCA in order to detect a significant (P < 0.05) increase in renal slice LDH leakage. Hepatic slices incubated with 0.5-2 mM 2,3-DCA or 2 mM 2,5-DCA exhibited diminished pyruvate-directed gluconeogenesis. After exposure to 2,4-DCA, 2,6-DCA, 3,4-DCA or 3,5-DCA, pyruvate-directed gluconeogenesis was similar to that in the controls. LDH leakage was increased significantly (P < 0.05) above control values by exposure to 2 mM 3,4-DCA or 3,5-DCA. In conclusion, DCA structural isomers were toxic in vitro to liver and kidney slices. These results indicated that the kidney was more sensitive than the liver to DCA isomers, and that the most toxic isomer was 3,5-DCA. These results are similar to those previously observed in vivo.

Acute renal and hepatic toxicity of 2-haloanilines in Fischer 344 rats

Aniline and its halogenated derivatives are widely used as chemical intermediates. The purpose of this study was to determine the hepatotoxic and nephrotoxic potential of the 2-haloanilines. Male Fischer 344 rats (n > or = 4) were injected (i.p.) with 1.0 or 1.25 mmol/kg of: aniline (A), 2-fluoroaniline (2-FA), 2-chloroaniline (2-ClA), 2-bromoaniline (2-BrA), 2-iodoaniline (2-IA) or vehicle (0.9% saline, 2.5 ml/kg). All compounds were injected as hydrochloride salts. Renal and hepatic function was monitored 24 h after treatment. All of the 2-haloanilines induced oliguria, diminished kidney weight, tubular casts and decreased renal cortical slice accumulation of organic anions. Blood urea nitrogen (BUN) levels were increased (P < 0.05) by treatment with 1.0 or 1.25 mmol/kg of 2-FA, 2-ClA or 2-BrA. Hepatic alterations were also observed and characterized by elevated plasma ALT/GPT activity and altered morphology in the centrilobular region. The nephrotoxic and hepatotoxic potentials were similar among the 2-haloanilines but aniline was less toxic than its 2-halo derivatives. These results demonstrated that halogen substitution at the 2-position of aniline increased hepatic and renal toxicity. However, the severity of toxicity was not influenced by the nature of the halogen substituent.

Haloaniline-induced in vitro nephrotoxicity: effects of 4-haloanilines and 3,5-dihaloanilines

Haloanilines are widely used as chemical intermediates in the manufacture of pesticides, dyes and drugs. The purpose of this study was to examine the in vitro nephrotoxic effects of the four 4-haloaniline and four 3,5-dihaloaniline isomers using renal cortical slices obtained from the kidneys of untreated, male Fischer 344 rats. Renal cortical slices were incubated with a haloaniline hydrochloride (0.1, 0.5, 1.0 or 2.0 mM, final concentration) or vehicle for 2 h, and toxicity determined by monitoring lactate dehydrogenase (LDH) release and changes in tissue gluconeogenesis capacity. At the concentrations tested, none of the 4-haloanilines increased LDH release. 4-Bromoaniline reduced gluconeogenesis at the lowest concentration (0.1 mM), but 4-iodoaniline 2.0 mM induced the largest decrease in gluconeogenesis (92% downward arrow). Among the 3,5-dihaloanilines, 3,5-dibromoaniline proved to be the most potent nephrotoxicant and 3,5-difluoroaniline the least potent nephrotoxicant. LDH release was increased by the dibromo (1.0 and 2. 0 mM), dichloro (2.0 mM) and diiodo (2.0 mM) derivatives, but not by 3,5-difluoroaniline. These results demonstrate that 3, 5-dihaloanilines are generally more potent nephrotoxicants in vitro than the 4-haloaniline isomers, and that bromo and iodo substitutions enhanced the nephrotoxic potential of aniline to the greatest degree.

Potentiation of 5-hydroxytryptamine-induced contraction in rat aorta by chlorpheniramine, citalopram and fluoxetine

This study examined the effects of chlorpheniramine, citalopram and fluoxetine on 5-hydroxytryptamine (5-HT)-induced contraction and 5-HT uptake in rat thoracic aortic rings in vitro. Chlorpheniramine and citalopram markedly potentiated 5-HT-induced contraction. Potentiation by fluoxetine was less pronounced. Chlorpheniramine (0.01-1 microM) and citalopram (0.1-1 microM) induced concentration-dependent parallel shifts to the left of the 5-HT concentration-response curves. The potentiation by chlorpheniramine was selective as chlorpheniramine (1 microM) did not potentiate phenylephrine-induced contraction. The potentiation did not depend upon the presence of endothelium, and was not related to H1 receptor antagonism as diphenhydramine and pyrilamine (1 microM) did not similarly enhance 5-HT-induced contractions. Whereas cocaine (1-10 microM) similarly potentiated 5-HT-induced contraction, imipramine (1-10 microM) inhibited, rather than enhanced, contraction elicited by 5-HT. In the presence of 10 microM cocaine, maximally effective concentrations of chlorpheniramine (1 microM) or citalopram (100 nM) did not induce any additional potentiation of 5-HT-induced contraction. Cooling (4 degrees C) markedly inhibited uptake of [3H]5-HT in rings with and without endothelium. Although less marked, imipramine (10 microM), cocaine (1 microM), chlorpheniramine (1 microM) and citalopram (100 nM) inhibited [3H]5-HT uptake in endothelium-intact and endothelium-denuded rings. Fluoxetine also inhibited [3H]5-HT uptake, but the inhibition was only statistically significant in endothelium-intact rings. The monoamine oxidase (MAO) inhibitor, pargyline (10-100 microM), did not significantly affect 5-HT-induced contraction. The results demonstrate that chlorpheniramine, citalopram and to a lesser extent, fluoxetine potentiate 5-HT-induced contraction in rat aorta in which neuronal 5-HT uptake is negligible. The data are consistent with inhibition of non-neuronal 5-HT uptake as at least one mechanism responsible for potentiation of 5-HT-induced contraction in rat aorta by chlorpheniramine, citalopram and fluoxetine.

In vitro nephrotoxicity induced by chloronitrobenzenes in renal cortical slices from Fischer 344 rats.

Chloronitrobenzenes are important chemical intermediates in the manufacture of industrial, agricultural and pharmaceutical agents. Toxicity induced by the various chloronitrobenzene isomers in vivo includes hematotoxicity, immunotoxicity, hepatotoxicity and nephrotoxicity. The purpose of the study was to determine the direct nephrotoxic effects of nitrobenzene and ten chlorinated nitrobenzene derivatives using renal cortical slices as the in vitro model. Renal cortical slices were prepared from kidneys of untreated, male Fischer 344 rats and incubated with nitrobenzene (1.0-5.0 mM), a chloronitrobenzene (0.5-5.0 mM) or vehicle for 2 h. At the end of the 2 h incubation, tissue gluconeogenesis capacity (pyruvate-stimulated gluconeogenesis) and lactate dehydrogenase (LDH) release were determined as measures of cellular function and cytotoxicity. Based on decreased pyruvate-stimulated gluconeogenesis and increased LDH release, the order of decreasing nephrotoxic potential was trichloronitrobenzenes>dichloronitrobenzenes>monochloronitrobenzenes>nitrobenzene. Among the mono- and dichloronitrobenzenes, 1-chloro-3-nitrobenzene and 3,4-dichloronitrobenzene were the most potent nephrotoxicants, while the two trichloronitrobenzenes tested exhibited similar nephrotoxic potentials. These results demonstrate that chloronitrobenzenes are directly nephrotoxic in vitro and that increasing the number of chloro groups increases the nephrotoxic potential of the resulting chloronitrobenzene derivative.

In vitro nephrotoxicity induced by propanil.

Propanil is a postemergence herbicide used primarily in rice and wheat production in the United States. The reported toxicities for propanil exposure include methemoglobinemia, immunotoxicity, and nephrotoxicity. A major metabolite of propanil, 3,4‐dichloroaniline (3,4‐DCA), has been shown to be a nephrotoxicant in vivo and in vitro, but the nephrotoxic potential of propanil has not been examined in detail. The purpose of this study was to determine the nephrotoxic potential of propanil using an in vitro kidney model, determine whether in vitro propanil nephrotoxicity is due to metabolites arising from propanil hydrolysis, and examine mechanistic aspects of propanil nephrotoxicity in vitro. Propanil, 3,4‐DCA, propionic acid (0.1–5.0 mM), or vehicle was incubated for 15–120 min with isolated renal cortical cells (IRCC; ∼4 million cells/mL) obtained from untreated male Fischer 344 rats. Cytotoxicity was determined by measuring lactate dehydrogenase release from IRCC. In 120‐min incubations, propanil induced cytotoxicity at concentrations >0.5 mM. At 1.0 mM, propanil induced cytotoxicity following 60‐ or 120‐min exposure. Cytotoxicity was observed with 3,4‐DCA (2.0 mM) at 60 and 120 min, while propionic acid (5.0 mM) induced cytotoxicity at 60 min. In IRCC pretreated with an antioxidant, cytochrome P450(CYP) inhibitor, flavin adenine dinucleotide monooxygenase activity modulator, or cyclooxygenase inhibitor before propanil exposure (1.0 mM; 120 min), only piperonyl butoxide (0.1 mM), a CYP inhibitor, pretreatment decreased propanil cytotoxicity. These results demonstrate that propanil is an in vitro nephrotoxicant in IRCC. Propanil nephrotoxicity is not primarily due to metabolites resulting from hydrolysis of propanil, but a metabolite resulting from propanil oxidation may contribute to propanil cytotoxicity.

Nephrotoxic potential of 2-amino-5-chlorophenol and 4-amino-3-chlorophenol in Fischer 344 rats: comparisons with 2- and 4-chloroaniline and 2- and 4-aminophenol☆

Nephrotoxicity occurs following intraperitoneal (i.p.) administration of 2-chloroaniline or 4-chloroaniline hydrochloride to Fischer 344 rats, but the nephrotoxicant chemical species and mechanism of nephrotoxicity are unknown. The purpose of this study was to evaluate the in vivo and in vitro nephrotoxic potential of 2-amino-5-chlorophenol and 4-amino-3-chlorophenol, metabolites of 4-chloroaniline and 2-chloroaniline. A comparison was also made between the nephrotoxic potential of the aminochlorophenols and the corresponding aminophenols to examine the effect of adding a chloride group on the nephrotoxic potential of the animophenols. Male Fischer 344 rats (4/group) were given an i.p. injection of a chloroaniline or aminochlorophenol hydrochloride (1.5 mmol/kg), and aminophenol (1.0 or 1.5 mmol/kg), or vehicle, and renal function monitored at 24 and 48 h. Both aminochlorophenols induced smaller and fewer renal effects that the parent chloroanilenes in vivo. Also, 4-aminophenol was markedly more potent as a nephrotoxicant that 4-amino-3-chlorophenol, while 2-aminophenol and 2-amino-5-chlorophenol induced only mild change in renal function. In vitro, the phenolic compounds reduce p-aminohippurate accumulation by renal cortical slices at bath concentrations of 0.01 mM, while a bath concentration of 0.50 mM or greater was required for the chloroanilines. However, all compounds reduced tetraethylammonium accumulation at bath concentrations of 0.1-0.5 mM or greater. These results indicate that extrarenally-produced aminochlorophenol metabolites do not contribute to the mechanism of chloroaniline nephrotoxicity. Also, the reduced nephrotoxic potential of 4-amino-3-chlorophenol compared to 4-aminophenol could result from an altered ability of the aminochlorophenol to redox cycle or form conjugates.

In vivo and in vitro 4-amino-2,6-dichlorophenol nephrotoxicity and hepatotoxicity in the Fischer 344 rat☆

Halogenated anilines and aminophenols are nephrotoxicants and hepatotoxicants in mammals. The purpose of this study was to determine the in vivo and in vitro nephrotoxic and hepatotoxic potential of 4-amino-2,6-dichlorophenol, a putative metabolite of 3,5-dichloroaniline. In the in vivo experiments, male Fischer 344 rats (four/group) were administered a single intraperitoneal (i.p.) injection of 4-amino-2,6-dichlorophenol (0.25, 0.38 or 0.50 mmol/kg) or vehicle (dimethylsulfoxide (DMSO), 1.0 ml/kg) and renal and hepatic function monitored for 48 h. Only minor changes in function or morphology were observed in the 0.25 mmol/kg treatment group. However, in the 0.38 mmol/kg treatment group evidence of both nephrotoxicity and hepatotoxicity were evident. Nephrotoxicity was characterized by increased proteinuria, glucosuria, hematuria, elevated blood urea nitrogen (BUN) concentration and kidney weight, decreased p-aminohippurate (PAH) accumulation and proximal tubular necrosis in the corticomedullary region of the kidney. Hepatotoxicity was characterized by elevated plasma alanine aminotransferase (ALT/GPT) activity and liver weight. Animals administered the 0.5 mmol/kg dose died within 24 h. In the in vitro experiments, the effect of 4-amino-2,6-dichlorophenol on organic ion accumulation, gluconeogenesis and lactate dehydrogenase (LDH) leakage was quantitated in liver and/or renal cortical slices. Organic anion accumulation was inhibited in renal cortical slices by 4-amino-2,6-dichlorophenol bath concentrations of 5 x 10(-6) M or higher, while organic cation uptake was decreased at 4-amino-2,6-dichlorophenol bath concentrations of 1 x 10(-5) M or greater. Renal and hepatic pyruvate-stimulated gluconeogenesis were inhibited and renal LDH leakage increased at 4-amino-2,6-dichlorophenol bath concentrations of 5 x 10(-5) M or greater. Increased LDH leakage from liver slices was not observed. These results demonstrate that 4-amino-2,6-dichlorophenol is a nephrotoxicant and hepatotoxicant in vivo and in vitro and that the kidney is more susceptible to 4-amino-2,6-dichlorophenol toxicity than the liver.

Effect of glucuronidation substrates/inhibitors on N-(3,5-dichlorophenyl)succinimidenephrotoxicity 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.

Effects of sodium sulfate on acute N-(3,5-dichlorophenyl)succinimide (NDPS) nephrotoxicity in the Fischer 344 rat

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces acute polyuric renal failure in rats. Results of previous studies have suggested that NDPS may induce nephrotoxicity via conjugates of NDPS metabolites. Thus, the purpose of this study was to examine if administered sodium sulfate could alter NDPS nephrotoxicity. Male Fischer 344 rats (four rats per group) were administered a single intraperitoneal (i.p.) injection of sodium sulfate (0.035, 0.07, 0.35 or 3.5 mmol/kg) or sodium chloride (7.0 mmol/kg) 20 min before NDPS (0.2, 0.4 or 0.8 mmol/kg) or NDPS vehicle (sesame oil, 2.5 ml/kg) and renal function monitored at 24 and 48 h. High dose sodium sulfate (3.5 mmol/kg) markedly attenuated NDPS nephrotoxicity, while sodium chloride had no effect on NDPS-induced renal effects. NDPS nephrotoxicity was also attenuated by a pretreatment dose of 0.35 mmol/kg sodium sulfate, while 0.07 mmol/kg sodium sulfate pretreatment potentiated NDPS 0.2 mmol/kg to produce nephrotoxicity without markedly attenuating NDPS 0.4 mmol/kg to induce renal effects. A dose of 0.035 mmol/kg sodium sulfate did not potentiate NDPS 0.2 mmol/kg to induce nephrotoxicity. These results suggest that sulfate conjugates of NDPS metabolites might contribute to NDPS nephrotoxicity.