Correlation of Therapeutic Effect of Obidoxime and Dosing Time in the Acute Intoxication by Chlorfenvinphos in Rats

Abstract: The ability of obidoxime with atropine and diazepam mixture to reactivate acetylcholinesterase inhibited by the organophosphorus compound chlorfenvinphos was compared in the central nervous system and peripheral tissues of rats. The animals were intoxicated with chlorfenvinphos (6 mg/kg, p.o.) and treated immediately, 24 and 48 hrs later with obidoxime (50 mg/kg, i.p.), atropine (10 mg/kg, i.p.), and diazepam (10 mg/kg, i.p.) in a single dose, or in various combinations (with 2–3 drugs) simultaneously. Total tissue acetylcholinesterase activities were monitored at 2, 72, and 168 hrs after intoxication. Enzyme activity was determined using Ellman's colorimetric method. The results of the present study show that obidoxime administered separately and jointly with atropine and diazepam 24 hrs after intoxication was effective on reactivation of chlorfenvinphos‐inhibited acetylcholinesterase in the central nervous system and in the peripheral tissues. However, the application of obidoxime alone or in combination with atropine and diazepam 48 hrs after chlorfenvinphos intoxication caused an increased unfavourable effect in rats. The results obtained also indicate an unfavourable interaction of obidoxime with diazepam in the course of chlorfenvinphos poisoning, when antidotes were administered immediately, 24 and 48 hrs after intoxication.     

Dose Dependence of Covalent Binding of Acrylonitrile to Tissue Protein and Globin in Rats

The dose dependence of acrylonitrile (AN) covalent binding totissue protein, following a single acute exposure over a 100-foldrange in dose, was measured. Covalent binding was a linear functionof AN dose in the lower dose range (0.0–0.95 mmol AN/kg).The slopes of the dose-response curves indicated that tissuesvaried by nearly 10-fold in their reactivity with AN. The relativeorder of covalent binding was as follows: blood > kidney= liver > forestomach = brain > glandular stomach >muscle. Similar dose-response behavior was observed for globintotal covalent binding and for globin N-(2-cyanoethyl)vallne(CEValine) adduct formation. The latter adduct was found torepresent only 0.2% of the total AN adduction to globin. Regressionof tissue protein binding versus globin total covalent bindingor globin CEValine adduct indicated that both globin biomarkerscould be used as surrogates to estimate the amount of AN boundto tissue protein. At higher AN doses, above approximately 1mmol/kg, a sharp break in the covalent binding dose-responsecurve was observed. This knot value is explained by the nearlycomplete depletion of liver glutathione and the resultant terminationof AN detoxification. The toxicity of AN is known to increasesharply above this dose. The data suggest that a comparisonof specific tissue proteins labeled by AN above and below thisthreshold dose may provide some insight into the mechanism ofAN-induced toxicity.     

Hyperbaric Oxygen Treatment Reduces Mortality in Acute Iron Intoxication in Rats

Abstract: Acute iron intoxication is one of the leading causes of overdose morbidity and mortality in children. The toxicity of iron has been postulated to be related to free radical formation and subsequent lipid peroxidation. Hyperbaric oxygen treatment can result in a number of beneficial biochemical, cellular and physiological effects, and has recently been shown to induce cellular protection against ischaemia, and in some cases against free radical formation. In the current study, we aimed to investigate the effects of hyperbaric oxygen treatment on mortality in acute iron intoxication in rats. After iron administration, 57 animals were divided into two groups: a treatment group receiving hyperbaric oxygen treatment (n = 30) and a control group (n = 27), and followed for 48 hr for signs of severe intoxication. In the second part of the study, 21 animals were divided into a treatment group receiving hyperbaric oxygen treatment (n = 10) and a control group (n = 11), and markers of oxidative stress were evaluated. We showed a significant reduction in mortality in hyperbaric oxygen‐treated animals from 17 of 27 (62.9%) among untreated rats to 6 of 30 (20%). Surprisingly, in the treatment group, levels of oxidative stress markers were higher. We postulate that hyperbaric oxygen has a potentially beneficial effect in acute iron intoxication.     

Effectiveness of Chelation Therapy with Time after Acute Uranium Intoxication

Effectiveness of Chelation Therapy with Time after Acute UraniumIntoxication. DOMINGO, J. L, ORTEGA, A., LLOBET, J. M., ANDCORBELLA, J. (1990). Fundam. Appl. Toxicol 14, 88–95.The effect of increasing the time interval between acute uraniumexposure and chelation therapy was studied in male Swiss mice.Gallic acid, 4,5-dihydroxy-l,3-benzenedisulfonicacid (Tiron),diethylenetriaminepentaacetic acid (DTPA), and 5-aminosalicylicacid (5-AS) were administered ip at 0,0.25, 1,4, and 24 hr aftersc injection of 10 mg/kg of uranyl acetate dihydrate. Chelatingagents were given at doses equal to one-fourth of their respectiveLD50 values. Daily elimination of uranium into urine and feceswas determined for 4 days after which time the mice were killed,and the concentration of uranium was measured in kidney, spleen,and bone. The excretion of uranium was especially rapid in thefirst 24 hr. Treatment with Tiron or gallic acid at 0, 0.25,or 1 hr after uranium exposure significantly increased the totalexcretion of the metal. In kidney and bone, only administrationof Tiron at 0,0.25, or I hr after uranium injection, or gallicacid at 1 hr after uranium exposure significantly reduced tissueuranium concentrations. Treatment at later times (4 to 24 hr)did not increase the total excretion of the metal and did notdecrease the tissue uranium concentrations 4 days after uranylacetate administration. The results show that the length oftime before initiating chelation therapy for acute uranium intoxicationgreatly influences the effectiveness of this therapy.     

急性氰戊菊酯中毒大鼠BALF和血清免疫生化反应的时间效应

本文报道大鼠经气管染毒4.66mg/kg氰戊菊酯后,不同时间BALF与血清免疫生化反应。4h时,BALA中LDH、MDH、Tpr、ALb、IgA、IgG和IgM含量均显著升高,血清仅IgM升高,而TPr和ALb显著下降。这些反应的达峰时间一般在34～96h。4～1:d,各参数值渐恢复至正常水平。结果提示,4.66mg/kg氰戊菊酯可诱导急性肺损伤,抑制或破坏肝细胞的蛋白质合成功能。     

Tissue Repair Response as a Function of Dose during Trichloroethylene Hepatotoxicity

Trichloroethylene (TCE), a widely used organic solvent and degreasingagent, is regarded as a hepatotoxicant. The objective of thepresent studies was to investigate whether the extent and timelinessof tissue repair has a determining influence on the ultimateoutcome of hepatotoxicity. Male Sprague-Dawley rats (200–250g) were injected with a 10-fold dose range of TCE and hepatotoxicityand tissue repair were studied during a time course of 0 to96 h. Light microscopic changes as evaluated by H&E-stainedliver sections revealed a dose-dependent necrosis of hepaticcells. Maximum liver cell necrosis was observed at 48 h afterthe TCE administration. However, liver injury as assessed byplasma sorbitol dehydrogenase (SDH) showed a dose response overa 10-fold dose range only at 6 h, whereas alanine aminotrans-ferase(ALT) did not show a dose response at any of the time pointsstudied. A low dose of TCE (250 mg/kg) showed an increase inSDH at all time points up to 96 h without peak levels, whereashigher doses showed peak only at 6 h. At later time points SDHdeclined but remained above normal. In vitro addition of trichloroaceticacid, a metabolite of TCE to plasma, decreased the activitiesof SDH and ALT indicating that metabolites formed during TCEtoxicity may interfere with plasma enzyme activities in vivo.This indicates that the lack of dose-related increase in SDHand ALT activities may be because of interference by the TCEmetabolite. Tissue regeneration response as measured by [³H]thymidineincorporation into hepatocellular nuclear DNA was stimulatedmaximally at 24 h after 500 mg/kg TCE administration. A higherdose of TCE led to a delay and diminishment in [³H]thymidineincorporation. At a low dose of TCE (250 mg/kg) [³H]thymidineincorporation peaked at 48 h and this could be attributed tovery low or minimal injury caused by this dose. With higherdoses tissue repair was delayed and attenuated allowing forunrestrained progression of liver injury. These results supportthe concept that the toxicity and repair are opposing responsesand that a dose-related increase in tissue repair representsa dynamic, quantifiable compensatory mechanism.     

Teratogenicity of 2-Methoxyethanol Applied as a Single Dermal Dose to Rats

Teratogenicity of 2-Methoxyethanol Applied as a Single DermalDose to Rats. FEUSTON, M. H., KERSTETTER, S. L., AND WILSON,P. D. (1990). Fundam. Appl Toxicol. 15, 448–456. 2-Methoxyethanol(2-ME) was applied as a single dermal dose on the backs of collared,pregnant Sprague-Dawley rats on Gestation Days (GD) 10, 11,12, 13, or 14 at doses of 0 and 2000 mg/ kg, and at doses of0, 250, 500, and 1000 mg/kg on GD 12. Except for a transientloss in body weight observed the day after 2-ME administration,no signs of maternal toxicity were observed. On GD 20, damswere necropsied and the fetuses evaluated for normal developmentResorp-tions were significantly (p < 0.05) increased in damsexposed to 2-ME on GD 10. Fetal body weights were reduced atdose levels of 1000 and 2000 mg/kg, but statistically significantdifferences were found only on GD 10 and 12. Significant increasesin external, visceral, and skeletal malformations were observedin fetuses exposed to 2-ME at dose levels of 500 mg/kg or greater.Defects of the cardiovascular and urinary systems were the prominentvisceral malformations observed. Limb defects (especially thosepertaining to the digits) and vertebral column defects (primarilyof the tail) were the most frequently observed skeletal defects.At the 2000 mg/kg dose level, 2-ME was teratogenic regardlessof the GD of administration. Based on the results of this study,the no observed adverse effect level for developmental toxicityfor a single dermal dose of 2-ME applied on GD 12 was determinedto be 250 mg/kg.     

A Role for Corticosterone in Impaired Intestinal Immunity and Barrier Function in a Rodent Model of Acute Alcohol Intoxication and Burn Injury

Alcohol (EtOH) intoxication and burn injury independently activate hypothalamic-pituitary-adrenal (HPA) axis, and glucocorticoids, the end product of the HPA axis, play a role in shaping the immune response under those conditions. By utilizing a rat model of acute EtOH intoxication and burn injury, studies in our laboratory have investigated the role of corticosterone (i.e., glucocorticoids in rodents) in altered intestinal immunity and barrier function following a combined insult of EtOH and burn injury. Results from these studies suggest that EtOH intoxication prior to burn injury augments corticosterone release, which in turn suppresses intestinal T cell function by inhibiting mitogen-activated protein kinase (i.e., p38 and ERK) pathway. Furthermore, we found that corticosterone does not directly alter the intestinal barrier function; rather, it up-regulates interleukin-18, which then directly or indirectly contributes to impaired intestinal barrier function. The loss of intestinal immunity/barrier function may result in increased bacterial translocation and thereby contribute to postinjury pathogenesis, leading to sepsis and organ dysfunction in burn patients as well as in patients with a history of EtOH intoxication.     

The Effects of Carbidopa Dose and Time and Route of Administration on Systemic L-Dopa Levels in Rats

The effects of carbidopa dose and time and route of administration on systemic plasma levels of parenterally and nonparenterally administered L-dopa were examined in rats. Intravenous coadministration of L-dopa + carbidopa resulted in significant (P < 0.05) carbidopa-dependent increases in both the area under the plasma L-dopa concentration versus time profile (AUC; +27%) and the plasma L-dopa half-life ( . Simultaneous duodenal or rectal carbidopa administration did not alter the L-dopa i.v. pharmacokinetic profile. Carbidopa pretreatment significantly increased the i.v. L-dopa AUC ( + 38 and +82% for i.v. and duodenal pretreatments, respectively) compared to simultaneous administration. Both i.v. and duodenal carbidopa increased duodenal L-dopa AUC to a similar extent ( + 282 and +239% for i.v. and duodenal administration, respectively). Rectal studies indicated poor absorption of both L-dopa and carbidopa, with no demonstrable effect on plasma L-dopa. The results indicate that the timing and route of carbidopa and L-dopa administration are important in determining the extent of i.v. or duodenal L-dopa systemic availability. The rat model affords results similar to those reported in human studies and may be useful for more extensive evaluation of L-dopa and carbidopa interactions.     

Enhancement of Pancreatic and Hepatic Glutathione Levels in Rats during Cyanohydroxybutene Intoxication

Enhancement of Pancreatic and Hepatic Glutathione Levels inRats during Cyanohydroxybutene Intoxication. WALLIG, M. A.,AND JEFFERY, E. H. (1990) Fundam. Appl. Toxicol. 14, 144–159.l-Cyano-2-hydroxy-3-butene (CHB), a cruciferous plant product,is hepatotoxic, pancreatotoxic, and elevates glutathione (GSH)in liver and pancreas. Whether GSH elevation is preceded bya depletion related to toxic insult, or whether toxicity andGSH elevation are unrelated, is not known. To evaluate the temporalrelationship between toxicity and GSH levels, male Fisher 344rats (6/group) were given CHB (200 mg/kg po) and killed up to96 hr after dosing. At death, histological and ultrastructuralevaluations and GSH/GSSG determinations were performed on liverand pancreas. In pancreas, dilatation of the cisternae of therough endoplasmic reticulum (RER) was evident from 2 hr, becomingprogressively more severe 4 and 6 hr after CHB. Frank apoptosisand loss of zymogen granules was evident by 6 hr, becoming widespreadby 12 hr. Recovery had commenced by 72 hr, and 50% of treatedrats had normal pancreata by 96 hr. No hepatic lesions wereobserved at this dose. Pancreatic GSH was depressed below 20%at 2 and 4 hr, rose to a maximum of 540% by 12 hr, and remainedelevated in treated rats throughout the study (275% at 96 hr).Hepatic GSH only fell to 50%, rose to 150-180%, and returnedto normal by 96 hr. While this pattern of depletion and reboundfollowing exposure to hepatotoxins is common, the exaggeratedand persistent elevation of pancreatic GSH is unprecedented.     

Time Course of Serum S100B Protein and Neuron‐Specific Enolase Levels of a Single Dose of Chlorpyrifos in Rats

Abstract: Organophosphate (OP) compounds are a large class of chemicals, many of which are used as pesticides. It is suggested that OPs specifically affect glia and neurons. Effects of acute exposure to chlorpyrifos (CPF), which is a common organophosphorus pesticide used worldwide, on neuron‐specific enolase (NSE) and S100B levels in rat blood during 7 days were assessed. Rats were evaluated either before (0 hr) or 2, 12, 24, 48 and 168 hr (7 days) after injection of CPF (279 mg/kg, s.c.) or vehicle (peanut oil, 2 ml/kg, s.c.) for clinical signs of toxicity. Immediately after the evaluation of toxicity, blood samples were taken for biochemical assays. CPF administration produced decreases in body‐weight and temperature, which were observed for first time at 12 hr after CPF administration and continued for 168 hr (p < 0.05–0.001). Serum S100B and NSE levels were acutely increased 2 hr after CPF administration and remained high at 12 hr (p < 0.01–0.001). NSE and S100B levels were not different in either CPF or vehicle groups at following time points. Serum butyrylcholinesterase (EC 3.1.1.8; BuChE) activity was dramatically reduced at 2 hr after CPF and remained low at each time points during 7 days (p < 0.01–0.001). Our results suggest that the usefulness of serum levels of these glia‐ and neuron‐specific marker proteins in assessing OP toxicity, specifically CPF‐induced toxicity.     

Temporal Changes in Tissue Repair Permit Survival of Diet-Restricted Rats from an Acute Lethal Dose of Thioacetamide

Although, diet restriction (DR) has been shown to substantiallyincrease longevity while reducing or delaying the onset of agerelateddiseases, little is known about the mechanisms underlying thebeneficial effects of DR on acute toxic outcomes. An earlierstudy (S. K. Ramaiah et al., 1998, Toxicol. Appl. Pharmacol.150, 12–21) revealed that a 35% DR compared to ad libitum(AL) feeding leads to a substantial increase in liver injuryof thioacetamide (TA) at a low dose (50 mg/kg, ip). Higher liverinjury was accompanied by enhanced survival. A prompt and enhancedtissue repair response in DR rats at the low dose (sixfold higherliver injury) occurred, whereas at equitoxic doses (50 mg/kgin DR and 600 mg/kg in AL rats) tissue repair in AL rats wassubstantially diminished and delayed. The extent of liver injurydid not appear to be closely related to the extent of stimulatedtissue repair response. The purpose of the present study wasto investigate the time course (0–120 h) of liver injuryand liver tissue repair at the high dose (600 mg TA/kg, ip,lethal in AL rats) in AL and DR rats. Male Sprague-Dawley rats(225–275 g) were 35% diet restricted compared to theirAL cohorts for 21 days and on day 22 they received a singledose of TA (600 mg/kg, ip). Liver injury was assessed by plasmaALT and by histopathological examination of liver sections.Tissue repair was assessed by [³H]thymidine incorporation intohepatonuclear DNA and proliferating cell nuclear antigen (PCNA)immunohistochemistry during 0–120 h after TA injection.In AL-fed rats hepatic necrosis was evident at 12 h, peakedat 60 h, and persisted thereafter until mortality (3 to 6 days).Peak liver injury was approximately twofold higher in DR ratscompared to that seen in AL rats. Hepatic necrosis was evidentat 36 h, peaked at 48 h, persisted until 96 h, and returnedto normal by 120 h. Light microscopy of liver sections revealedprogression of hepatic injury in AL rats whereas injury regressedcompletely leading to recovery of DR rats by 120 h. Progressionof injury led to 90% mortality in AL rats vs 30% mortality inDR group. In the surviving AL rats, S-phase DNA synthesis wasevident at 60 h, peaked at 72 h, and declined to base levelby 120 h, whereas in DR rats S-phase DNA synthesis was evidentat 36 h and was consistently higher until 96 h reaching controllevels by 120 h. PCNA studies showed a corresponding increasein cells in S and M phase in the AL and DR groups. DR resultedin abolition of the delay in tissue repair associated with thelethal dose of TA in ad libitum rats. Temporal changes and highertissue repair response in DR rats (earlier and prolonged) arethe conduits that allow a significant number of diet restrictedrats to escape lethal consequence.     

生物学标志的概念与应用

近年来,生物学标志在毒理学、流行病学等多学科中得到广泛的应用。本文综述了近年来有关生物学标志的概念和和分类,阐述了生物学标志的的检测,即直接检测接触物及其代谢产物,动物试验中毒代动力学资料的应用,人类生物样品中生物学标志的测定和毒代动力学中数学模型。其后阐述了大分子加合物重点是DNA加合物作为生物学标志的应用。     

Comparative Disposition of Acrylonitrile and Methacrylonitrile: Quantitative Whole-Body Autoradiographic Studies in Rats

Following intravenous administration of an equimolar (0.216mmol/kg) radioactive dose of acrylonitrile (2-[¹⁴C]VCN, 11.5mg/kg) or methacrylonitrile (2-[¹⁴C]MeVCN, 14.5 mg/kg), thetissue distribution, covalent interaction, and elimination werecompared (at 5 mm to 48 hr) in male Fischer 344 rats using whole-bodyautoradiography (WBA). Autoradiographs obtained from freezedriedor acid-extracted sections of animals treated with 2-[¹⁴C]VCNshowed that radioactivity accumulated in the liver, lung, bonemarrow, adipose tissues, kidney, gastrointestinal tract, andspleen. In animals treated with 2-[¹⁴C]MeVCN, the respiratorytissues contained high levels of ¹⁴C at an early period (5 min),while the gastrointestinal mucosa, adrenal cortex, liver, andkidney contained high levels of radioactivity at later periods(8, 24, and 48 hr). Quantitatively, lower uptake and irreversibleinteractions of ¹⁴C were observed in autoradiographs of ratstreated with 2-[¹⁴C]MeVCN, compared with those treated with2-[¹⁴C]VCN. Rats given 2-[¹⁴C]VCN eliminated only 27% of administeredradioactivity (exhaled air, urine, and feces), whereas ratstreated with 2-[¹⁴C]MeVCN eliminated, by all routes, 65% ofthe total radioactive dose. Both WBA and elimination studiesindicated that 2-[¹⁴C]VCN and/or its metabolites were rapidlydistributed, extensively bound, and slowly eliminated from tissues.2-[¹⁴C]MeVCN and/or its metabolites, however, were rapidly distributedand eliminated, mostly via the lung. The study indicated thatthe substitution of a methyl group on the -carbon of the –ßunsaturated aliphatic nitrile VCN, to form MeVCN, imparted qualitativeand quantitative differences in the disposition of these twocompounds.     

Lithium-induced Loss of Body Sodium and the Development of Severe Intoxication in Rats

Four groups of rats were given food containing 0, 40, 70, or 100 mmol LiCl per kg dry weight, respectively. They had free access to water and 0.46 M-NaCl. This regimen was maintained for one month, and the rats did not develop lithium intoxication in spite of the high lithium dosage. The rats given lithium-containing food drank more sodium chloride solution than the control rats, and the intake increased with the lithium content of the food. Access to sodium chloride solution was then discontinued. In the two groups given the highest lithium dosages this led within four days to a marked loss of body sodium and a proportionate loss of body weight, a significant decrease of serum sodium, and the development of severe lithium intoxication. Half of the rats in these groups died within 16 days. When rats with severe lithium intoxication were given access to 0.15 M-NaCl, they drank so much of the sodium chloride solution within one hour that their body weight prior to the intoxication was re-established. The experiments indicate that administration of lithium leads to a lowered ability of the kidneys to conserve sodium and a consequent increased requirement for sodium. If this is not fulfilled, the animals lose sodium and develop severe lithium intoxication.