Enzyme induction produced by N-(3,5-dichlorophenyl)succinimide (NDPS) in rats

Novel protective mechanisms for S-adenosyl-L-methionine against acetaminophen hepatotoxicity: improvement of key antioxidant enzymatic function

Acetaminophen (APAP) overdose leads to severe hepatotoxicity, increased oxidative stress and mitochondrial dysfunction. S-adenosyl-L-methionine (SAMe) protects against APAP toxicity at a mmol/kg equivalent dose to N-acetylcysteine (NAC). SAMe acts as a principle biological methyl donor and participates in polyamine synthesis which increase cell growth and has a role in mitochondrial protection. The purpose of the current study tested the hypothesis that SAMe protects against APAP toxicity by maintaining critical antioxidant enzymes and markers of oxidative stress. Male C57Bl/6 mice were treated with vehicle (Veh; water 15 ml/kg, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg, ip), and SAMe+APAP (SAMe given 1 h following APAP). Liver was collected 2 and 4 h following APAP administration; mitochondrial swelling as well as hepatic catalase, glutathione peroxidase (GPx), glutathione reductase, and both Mn- and Cu/Zn-superoxide dismutase (SOD) enzyme activity were evaluated. Mitochondrial protein carbonyl, 3-nitrotyrosine cytochrome c leakage were analyzed by Western blot. SAMe significantly increased SOD, GPx, and glutathione reductase activity at 4 h following APAP overdose. SAMe greatly reduced markers of oxidative stress and cytochrome C leakage following APAP overdose. Our studies also demonstrate that a 1.25 mmol/kg dose of SAMe does not inhibit CYP 2E1 enzyme activity. The current study identifies a plausible mechanism for the decreased oxidative stress observed when SAMe is given following APAP.

Acute renal and hepatic effects induced by 3-haloanilines in the Fischer 344 rat

Haloanilines are commonly used as chemical intermediates in the manufacture of a wide range of products. The purpose of this study was to examine the in vivo nephrotoxic and hepatotoxic potentials of the 3-haloanilines. The in vitro effects of the 3-haloanilines on renal function were also examined. In the in vivo experiments, male Fischer 344 rats (four rats/group) were administered a single intraperitoneal (i.p.) injection of an aniline hydrochloride (1.0 or 1.25 mmol kg-1) or vehicle. Renal and hepatic function were monitored at 24 and/or 48 h post-treatment. None of the 3-haloanilines were potent nephrotoxicants at either dose level. The greatest effects on renal function were observed following administration of 3-chloroaniline at a dose of 1.25 mmol kg-1 (oliguria, glucosuria, hematuria, decreased p-aminohippurate accumulation by renal cortical slices and increased blood urea nitrogen concentration). 3-Chloroaniline also was the only aniline compound to increase plasma ALT/GPT activity at 48 h. In the in vitro experiments, the ability of an aniline (10(-5) - 10(-3) M) to decrease organic ion accumulation in renal cortical slices from untreated rats was examined. The decreasing order of in vitro nephrotoxic potential was 3-iodoaniline > 3-bromoaniline > 3-chloroaniline > aniline > 3-fluoroaniline. These results indicate that the 3-haloanilines are not potent nephrotoxicants or hepatotoxicants at sublethal doses. In addition, the reasons why the 3-haloanilines have different orders of nephrotoxic potential in vivo and in vitro are not clear at this time.

The effects of cobalt chloride, SKF-525A, and N-(3,5-dichlorophenyl)succinimide on in vivo hepatic mixed function oxidase activity as determined by single-sample plasma clearances

1. Four drugs--antipyrine, theophylline, quinidine, and ethosuximide--were used as probes of in vivo hepatic mixed function oxidase (MFO) activity. Functional MFO activity was evaluated by estimating probe clearances subsequent to pretreatment of rats with either cobalt chloride, SKF-525A, or N-(3,5-dichlorophenyl) succiminide (NDPS). 2. Clearances of each probe were estimated from single plasma concentration measurements. Each pretreatment altered the clearances of this panel of probes in a different way. NDPS pretreatment increased theophylline clearance while slowing quinidine and ethosuximide clearances. SKF-525A slowed all probe clearances except for ethosuximide. Cobalt chloride slowed all probe clearances except for theophylline. 3. The use of multiple probes as substrates for the hepatic cytochrome P-450 system can provide some insight into the functional consequences of xenobiotic exposures on that system. Moreover, xenobiotic-induced functional changes on hepatic MFO when assessed in vivo appear to be modest relative to changes in in vitro activity or hepatic cytochrome P-450 content. This minimally invasive multiprobe method may be useful for assessing xenobiotic influences on human hepatic MFO in vivo.