L-buthionine (S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, was administered to mice via drinking water for 14 days in order to establish an animal model with continuously depleted levels of GSH. No toxicity was observed at 20 mM BSO, even though a significant decrease in liver weight was observed at 30 mM BSO. GSH levels in the liver, kidney, brain, lung, heart, spleen, pancreas, small intestine, large intestine, skeletal muscle, plasma and blood cells from mice given 20 mM of BSO were all less than those from the control mice continuously throughout a 24-hr period. The ratios of the GSH levels to that of the control were 46.4% and 16.7% in the liver and kidney, respectively, suggesting a decrease in GSH conjugation activity in vivo by GSH depletion. Liver cytochrome P450 content and UDP-glucuronosyltransferase activity to p-nitrophenol were not influenced by the BSO dosing. To confirm the adequacy of this GSH-depletion model, 0.125 or 0.25% of acetaminophen (APAP) was administered via diet to this model for 14 days. Nine out of the ten mice given both 20 mM BSO and 0.25% APAP died on Day 2, and remarkable necrosis was observed in the hepatocytes and renal tubular epithelium. Moreover, focal necrosis of hepatocytes with proliferation of fibroblasts was observed on Day 15 in some mice coadministered 20 mM BSO and 0.125% APAP. However, no toxicity was observed in mice given APAP alone. Based on these results, a mouse given 20 mM of BSO via drinking water for 14 days was concluded to be an animal model with continuously depleted levels of GSH in various organs without toxicity. This model shows high susceptibility to toxicity induced by chemicals which are metabolized to electrophilic and reactive metabolite(s), such as APAP.
Exocyclic small peptidomimetics corresponding to three critical binding sites of tumor necrosis factor (TNF)-receptor(I) have been designed based on atomic features deduced from the crystal structures of TNF alpha and the TNF beta/TNF-receptor(I) complex and a model of an anti-TNF alpha monoclonal antibody. TNF alpha antagonistic activities were evaluated by binding assays using soluble receptor or intact receptor on cells as well as an apoptosis/cytotoxicity assay. The most critical interaction site for rational design of peptidomimetics was localized to the loop1/domain3 of the TNF-receptor. The best antagonist showed 5 microM inhibition in the binding assay. Biologically, the mimetics inhibited TNF alpha-mediated apoptosis.
-A sensitive urinary biomarker for acute kidney injury (AKI) was investigated in beagle dogs with nephrotoxicity induced by gentamicin. Gentamicin sulphate at 25 or 50 mg/kg was injected (s.c.) for 9 days, and conventional urinalysis, ELISA assay of neutrophil gelatinase-associated lipocal (NGAL) in urine, blood chemistry, and pathological examinations were performed. The dog given gentamicin at 25 mg/kg only showed slight deposition of lysosomal granules in the proximal tubular epithelium of the kidneys without any other significant changes even though urinary NGAL was elevated on Day 10 (day of necropsy). In the dog receiving gentamicin at 50 mg/kg, increases in urinary NGAL were observed on Days 3 and 5, and absence of urination, marked increases in serum urea nitrogen and creatinine, enlargement and discoloration of the kidneys with marked necrosis, and swelling of proximal epithelium were observed. In conclusion, urinary NGAL is considered to be a candidate as a sensitive predictable biomarker of AKI in the gentamicin-induced nephrotoxicity model in dogs.Key words: NGAL, Dogs, Acute kidney injury, Urinary biomarker, Gentamicin Correspondence: Kiyonori Kai (E-mail: kai.kiyonori.xb@daiichisankyo.co.jp) LetterThe Journal of Toxicological Sciences (J. Toxicol. Sci.) Vol.38, No.2, 269-277, 2013 Vol. 38 No. 2 269 addition to these biomarkers, neutrophil gelatinase-associated lipocal (NGAL), a member of the lipocalin superfamily, has been proposed as a candidate for a sensitive urinary biomarker to detect AKI Mori, 2005;Mori and Nakao, 2007). Unfortunately, in part due to the lack of commercially available assays for non-rodents, limited data comparing the performance of the exploratory and approved markers are publicly available so far.In this study, we selected gentamicin, a well-known nephrotoxic agent that induces AKI in experimental animals and humans, and injected it subcutaneously to beagle dogs for 9 days and evaluated urinary NGAL using a commercial ELISA kit as a sensitive urinary biomarker in comparison with conventional blood and urinary toxicity makers and pathological examinations. MATERIALS AND METHODS Test articleELTACIN injection, an injectable product of gentamicin sulfate was purchased from FujiPharma (Shizuoka, Japan). Animals and housing conditionsTwo male beagle dogs were purchased from Narc Corporation (Chiba, Japan) for gentamicin treatment, and 6 males and 6 females were additionally obtained from Marshall BioResources, Japan (Ibaraki, Japan) for collection background data of urinalysis. The dogs were individually housed in stainless steel cages (W93.5 cm × W80 cm × H78.5 cm) in an air-conditioned room (temperature, 18 to 28°C; relative humidity, 30 to 70%). A light/dark cycle of 12 hr and ventilation rate of 10 to 20 air changes/ hr were used in the animal rooms. Two hundred and twenty grams of basal diet (Certified Canine Diet 5007, PMI Nutrition International, Inc., St. Louis, MO, USA) was given to each dog in the morning and tap water was available ad libitum. All experimen...
RS-8359, (+/-)-4-(4-cyanoanilino)-5,6-dihydro-7-hydroxy-7H-cyclopenta[d]pyrimidine selectively and reversibly inhibits monoamine oxidase A (MAO-A). After oral administration of rac-RS-8359 to rats, mice, dogs, monkeys, and humans, plasma concentrations of the (R)-enantiomer were greatly higher than were those of the (S)-enantiomer in all species studied. The AUC((R)) to AUC((S)) ratios were 2.6 in rats, 3.8 in mice, 31 in dogs, and 238 in monkeys, and the (S)-enantiomer was almost negligible in human plasma. After intravenous administration of RS-8359 enantiomers to rats, the pharmacokinetic parameters showed that the (S)-enantiomer had a 2.7-fold greater total clearance (CL(t)) and a 70% shorter half-life (t(1/2)) than those for the (R)-enantiomer but had no difference in distribution volume (V(d)). No significant difference in the intestinal absorption rate was observed. The principal metabolites were the 2-keto form, possibly produced by aldehyde oxidase, the cis-diol form, and the 2-keto-cis-diol form produced by cytochrome P450 in rats, the cis-diol form in mice, RS-8359 glucuronide in dogs, and the 2-keto form in monkeys and humans. Thus, the rapid disappearance of the (S)-enantiomer from the plasma was thought to be due to the rapid metabolism of the (S)-enantiomer by different drug-metabolizing enzymes, depending on species.
The 2-oxidation activity on the pyrimidine ring of RS-8359, a MAO-A inhibitor, is the major metabolic pathway catalysed by aldehyde oxidase. This study investigated the species differences in the 2-oxidation activity by using liver cytosolic fractions from rats, mice, guinea-pigs, rabbits, dogs, monkeys and humans. The Vmax/Km value for the (S)-enantiomer of RS-8359 was extremely high in monkeys and humans, moderate in guinea-pigs, and low in rats and mice. Dogs were deficient in 2-oxidation activity. The (R)-enantiomer was only oxidized at a very low rate in guinea-pigs, monkeys and humans, and not oxidized in rats, mice and rabbits. Thus, marked species differences and enantioselectivity were obvious for the 2-oxidation of the (S)-enantiomer of RS-8359. The in vitro results were in good accordance with previously reported in vivo excretion data of the 2-keto metabolite and the non-detectable plasma concentrations of the (S)-enantiomer in monkeys and humans after administration of racemic RS-8359. Enantioselectivity was also observed for the oxidation of cinchona alkaloids catalysed by aldehyde oxidase. Among the four cinchona alkaloids studied, the oxidation activity of cinchonidine, which has no substituents at the 6-hydroxy group but bears (8S,9R)-configurations, was highest. As opposed to the (S)-enantiomer, an extremely high catalytic activity of cinchonidine was confirmed in rabbits, but not in monkeys or humans. Rabbit liver aldehyde oxidase was suggested to have characteristic properties around the active site.
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