'Superwarfarins' as agents of accidental or deliberate intoxication.
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1. The hydrolysis of adenosine di- and monophosphate (ADP, AMP) was studied in perfused lungs isolated from rats treated with alpha-naphthylthiourea (ANTU) to induce acute lung injury. This injury is associated with damage to the endothelium, the locus of the ADP and AMP hydrolysing enzymes. 2. Treatment with ANTU did not change the proportion of [3H]-ADP surviving a single passage through the pulmonary circulation, at any time up to 50 h after ANTU. Less than 8% and 2% respectively of 1 or 0.1 mumol ADP, given as a bolus, appeared in lung effluent. 3. The metabolites of ADP, AMP and adenosine in lung effluent were increased fro 2 h after ANTU. 4. Metabolism of [3H]-AMP as substrate was always low but, following ANTU treatment, the adenosine content of lung effluent increased four fold. 5. It appears that, in spite of considerable endothelial cell damage, as demonstrated by pulmonary oedema, the ectoenzymes catalysing ADP and AMP hydrolysis were relatively little affected by ANTU.
1. The relationship between pharmacological response and disposition of a dose of vitamin K1 (10 mgkg-1, i.v.) in normal rabbits and in rabbits treated with the coumarin anticoagulant brodifacoum, has been studied. 2. High performance liquid chromatography (h.p.l.c.) with electrochemical detection (EC) was used to determine concentrations of vitamin K1 in plasma, whole liver homogenate, and liver microsomes. 3. After intravenous administration of vitamin K1, plasma concentrations of the vitamin declined in a tri-exponential fashion. There were no differences between the two groups over the first 24 h of the experiment. However, between 24 h and the end of the study, plasma concentrations of vitamin K1 in the presence of brodifacoum were significantly (P less than or equal to 0.05) below those of vehicle-treated rabbits. 4. Seventy-two hours after administration of vitamin K1, plasma concentrations of the vitamin were not different from normal. 5. Three hours after administration of vitamin K1, the concentrations of the vitamin in whole liver were 46.6 +/- 4.3 micrograms g-1 in the presence of brodifacoum, and 32.8 +/- 6.4 micrograms g-1 in the absence of brodifacoum; and were significantly (P less than or equal to 0.05) greater than normal (127.7 +/- 44.3 ng g-1). Likewise, microsomal concentrations of vitamin K1 (4.00 +/- 2.38 micrograms mg-1 protein, and 2.65 +/- 1.01 micrograms mg-1 protein, in the presence and absence of brodifacoum, respectively) were significantly (P less than or equal to 0.01) greater than normal (16.0 +/- 3.5 ng mg-1 protein). 6 In conclusion, there appears to be no direct effect of coumarins on clearance of vitamin K1 from either plasma or liver; the need for large doses of vitamin K1 during coumarin poisoning is due to a greatly increased requirement for the vitamin.
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The pharmacokinetics of 2-pivaloylindan-1,3-dione (Pival) after administration of a single dose was investigated in dogs. The plasma concentration graph can be described by a one compartment open model. The drug is fairly well adsorbed (67%) and the excretion is extremely slow with a half-life of nearly five days. These kinetics can be explained by the physiochemical properties of the drug, such as strong binding to canine plasma protein, high lipophility and the lack of transformation to polar metabolites. A single oral dose of 5 mg/kg must be regarded as lethal to dogs and the LD50 is assumed to be approximately 4 mg/kg in this species.
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The toxicity of pindone, a rabbit poison, to horses, cattle, goats, chickens, dogs and cats was investigated, using extension of prothrombin time (PT) as an index of poisoning. The daily dose of pindone, administered for 5 days, ranged from 0.3 mg/kg for dogs to 2.5 mg/kg for chickens. This range of dose rates was considered to be indicative of the worst possible case that could arise following a campaign of baiting for rabbits. Although significant elevations in PT (more than double baseline values) were noted in all species other than horses, clinical signs of anticoagulant poisoning were not observed in any of the species tested. From the observed PT, cattle and cats appeared to be the most susceptible, and horses the least susceptible, to pindone toxicity. The half-lives of the elevated PT were calculated as 3.1 days for cattle, 2.8 days for goats and chickens, 1.9 days for horses and dogs and less than one day for cats. It is proposed that these half-lives can be used as a guide for determining the duration of treatment of pindone-affected animals.
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Sodium monofluoroacetate (Compound 1080) is a widely used pesticide for control of feral animals such as the fox. Accidental poisoning of domestic animals occurs despite strict regulations on 1080 usage. Dogs are particularly susceptible to the toxin. The mechanism of 1080 toxicity, susceptibility of target and non-target species, persistence of 1080 in the environment and risk of accidental poisoning are discussed. Particular emphasis is placed on 1080 toxicity in the dog. Early recognition of intoxication is most important for prognosis and relies upon characteristic clinical signs and diagnostic findings. The treatment of 1080 intoxication remains a challenge with no proven antidotes. However, there are possible benefits from monoacetin, acetamide, calcium salts, colestipol, activated charcoal, peritoneal dialysis, sodium bicarbonate, neurotransmitter modulators and four-methylpyrazole. A recommended treatment protocol for 1080 toxicosis in dogs is included. Safety measures such as the use of wire dog muzzles and investigating alternatives to 1080 in pest control programs may be the key to reducing the incidence of future accidental poisonings.
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Rhodococcus sp. strain DN22 can convert hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to nitrite, but information on degradation products or the fate of carbon is not known. The present study describes aerobic biodegradation of RDX (175 microM) when used as an N source for strain DN22. RDX was converted to nitrite (NO(2)(-)) (30%), nitrous oxide (N(2)O) (3.2%), ammonia (10%), and formaldehyde (HCHO) (27%), which later converted to carbon dioxide. In experiments with ring-labeled [(15)N]-RDX, gas chromatographic/mass spectrophotometric (GC/MS) analysis revealed N(2)O with two molecular mass ions: one at 44 Da, corresponding to (14)N(14)NO, and the second at 45 Da, corresponding to (15)N(14)NO. The nonlabeled N(2)O could be formed only from -NO(2), whereas the (15)N-labeled one was presumed to originate from a nitramine group ((15)N-(14)NO(2)) in RDX. Liquid chromatographic (LC)-MS electrospray analyses indicated the formation of a dead end product with a deprotonated molecular mass ion [M-H] at 118 Da. High-resolution MS indicated a molecular formula of C(2)H(5)N(3)O(3). When the experiment was repeated with ring-labeled [(15)N]-RDX, the [M-H] appeared at 120 Da, indicating that two of the three N atoms in the metabolite originated from the ring in RDX. When [U-(14)C]-RDX was used in the experiment, 64% of the original radioactivity in RDX incorporated into the metabolite with a molecular weight (MW) of 119 (high-pressure LC/radioactivity) and 30% in (14)CO(2) (mineralization) after 4 days of incubation, suggesting that one of the carbon atoms in RDX was converted to CO(2) and the other two were incorporated in the ring cleavage product with an MW of 119. Based on the above stoichiometry, we propose a degradation pathway for RDX based on initial denitration followed by ring cleavage to formaldehyde and the dead end product with an MW of 119.
A unique metabolite with a molecular mass of 119 Da (C(2)H(5)N(3)O(3)) accumulated during biotransformation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Rhodococcus sp. strain DN22 (D. Fournier, A. Halasz, J. C. Spain, P. Fiurasek, and J. Hawari, Appl. Environ. Microbiol. 68:166-172, 2002). The structure of the molecule and the reactions that led to its synthesis were not known. In the present study, we produced and purified the unknown metabolite by biotransformation of RDX with Rhodococcus sp. strain DN22 and identified the molecule as 4-nitro-2,4-diazabutanal using nuclear magnetic resonance and elemental analyses. Furthermore, we tested the hypothesis that a cytochrome P450 enzyme was responsible for RDX biotransformation by strain DN22. A cytochrome P450 2B4 from rabbit liver catalyzed a very similar biotransformation of RDX to 4-nitro-2,4-diazabutanal. Both the cytochrome P450 2B4 and intact cells of Rhodococcus sp. strain DN22 catalyzed the release of two nitrite ions from each reacted RDX molecule. A comparative study of cytochrome P450 2B4 and Rhodococcus sp. strain DN22 revealed substantial similarities in the product distribution and inhibition by cytochrome P450 inhibitors. The experimental evidence led us to propose that cytochrome P450 2B4 can catalyze two single electron transfers to RDX, thereby causing double denitration, which leads to spontaneous hydrolytic ring cleavage and decomposition to produce 4-nitro-2,4-diazabutanal. Our results provide strong evidence that a cytochrome P450 enzyme is the key enzyme responsible for RDX biotransformation by Rhodococcus sp. strain DN22.