Study On Forensic Toxicokinetics Of Omethoate

OBJECTIVE:1. To establish the postmortem redistribution single-body animal models of omethoate in dogs;To establish the decomposition kinetics model of omethoate in preserved specimens and buriedcadaver of dogs.2. To investigate the postmortem redistribution of omethoate in dogs and the decompositionkinetics of omethoate in preserved specimens and buried cadaver of dogs; To provide a scientificevidence for the forensic identification of omethoate poisoning death.METHODS:1. Postmortem redistributionFour dogs were randomly allocated to postmortem redistribution group （n=3） and controlgroup （n=1）.The postmortem redistribution group dogs were given an intragastric administrationof omethoate with a dose of20LD₅₀. The samples such as heart blood, peripheral blood, brain,liver and right hindlimb muscle were collected at0h,2h,6h,12h,24h,48h,72h,96h and120hafter the death. The dog in control group was given the same volume of physiological saline, andthe blood and tissues were collected to be used as blank. The blood and tissues were extracted byMethylene chloride after added in the internal standard （malation）. Analysis was performed witha GC equipped with a FPD and a GC/MS.2. The decomposition kinetics in preserved specimens2.1decomposition kinetics of omethoate in preserved specimens of poisoned dogs:Six dogs were given an intragastric administration of omethoate with a dose of20LD₅₀.Then thetoxic symptoms were observed. As soon as the blood pressure, respiration and ECG disappeared,the dogs were dissected, and the specimens of blood and liver were sampled and divided intofour parts. Three of them were preserved at20℃,4℃,-20℃repectively. Another bloodcontaining1%NaF or liver fixed with4%formaldehyde solution were preserved at20℃.Omethoate in them were detected by the GC equipped with a FPD and a GC/MS on differenttime after the storage. The epuationand parameters of decomposition kinetics were imitated andcalculated with WinNonlin program.2.2decomposition kinetics of omethoate in preserved cadaver blood: Added5mL omethoate into1000mL cadaver blood and then divided into four parts. Three of them were preserved at20℃,4℃,-20℃repectively, another was preserved at20℃（1%NaF）. The omethoate in them were detected by the GC equipped with a FPD and a GC/MS on different time after the storage. Theepuationand parameters of decomposition kinetics were imitated and calculated with WinNonlinprogram.3. The decomposition kinetics in buried cadavers3.1The effection of buried time on the decomposition kinetics in buried cadavers: Thirty dogswere given an intragastric administration of omethoate with a dose of20LD₅₀.As soon as thedogs died, the dogs were put into plastic unsealed bags, and buried in the field in East Mountain,Taiyuan City. Three of them were dugged out, dissected and the specimens were collected foranalysis of omethoate on the0thd,29thd,59thd,120thd, and380thd after the burying. Theomethoate were detected qualitively and quantitative byGC and GC/MS.3.2The effection of poisonous dose on the decomposition kinetics in buried cadavers: twelvedogs were randomly allocated to three groups. Three of them were given an intragastricadministration of omethoate with dose of5LD₅₀and10LD₅₀.Six of them were given anintragastric administration with a dose of20LD₅₀.As soon as the dogs died, the dogs were putinto plastic unsealed bags, specimens were collected on the89thd and120thd after the burying.The omethoate were detected qualitively and quantitative by GC and GC/MS.3.3The effection of buried way on the decomposition kinetics in buried cadavers: nine dogswere given an intragastric administration of omethoate with a dose of20LD₅₀.As soon as thedogs died, the dogs were randomly allocated into three groups and put into plastic bags, wovenbags and wooden cases （coffins） respectively, then buried in the field in East Mountain, TaiyuanCity. They were dugged out, dissected and the specimens were collected for analysis ofomethoate on the75thd after the burying. The omethoate were detected qualitively andquantitative by GC and GC/MS.RESÎœLTS:1. Postmortem redistributionThe concentration of omethoate detected in heart blood was significantly higher than infemoral blood at0h and120h, the heart blood/femoral blood concentration ratios averaged1.87and1.10. Compared with the concentration at the death, the content of omethoate in bloodshowed a significant increase during24h-72h after the death （P<0.05）, the postmortem/deathheart blood concentration ratios averaged1.20-1.32; The liver concentration of omethoateshowed a significant increase at12h-48h after the death （P<0.05）, the postmortem/death liverblood concentration ratios averaged1.47-1.62; The concentration in muscle was descending at72h-96h, there was no significant change in brain （P>0.05）.2. The decomposition kinetics in preserved specimens2.1decomposition kinetics of omethoate in preserved blood and liver of poisoned dogs The concentration of omethoate detected in preserved specimens showed a descended trendin each condition. The content of omethoate in blood at20℃,20℃（1%NaF）,4℃,-20℃descended significantly to11.7±4.6%,8.1±1.6%,51.9±12.1%,69.2±26.9%（P﹤0.05）ofinitial concentration on10thd,12thh,23thd,23thd respectively. After stored29d,60h,110d and110d, the content of omethoate in blood descended to0.5±0.004%,0.5±0.001%,3.0±0.1%,4.6±2.4%of initial concentration respectively. After stored by72h, omethoate has not beendetected in blood at20℃（1%NaF）.The content of omethoate in liver at20℃,20℃（4%formaldehyde solution）,4℃,-20℃preserved on2thd,10thh,10thd,23thd were significantly descended to56.9±0.2%,25.4±6.8%,61.1±9.3%,52.1±9.6%（P﹤0.05）separately, and preserved on29thd,110thh,110thd,110thd,the content of omethoate have been descended to1.6±0%,2.7±0.7%,7.2±5.4%,10.4±1.5%of initial concentration. After stored by31d, omethoate has not been detected in liver at20℃.The decomposition kinetics of omethoate in each condition fit to the first-order kineticsprocess, and could be expressed as Ctt=Coe-α+C1e-βtand C-αtt=Coe.20℃,-20℃blood groups and4℃liver group fit to a one compartment open model with a first-order kinetics and could beexpressed as Ct=Coe-αt, the fast decomposion half-lifes(t_1/2α) of omethoate were4.5d,33.6d and30.2d;4℃,20℃（1%NaF） blood groups and20℃,20℃（4%formaldehyde solution）,-20℃liver groups fit to the two compartment open model with a first-order kinetics and could beexpressed as Cαtt=Coe-+C-1eβt, the fast and slow decomposion half-lifes（t1/2αand t1/2β） ofomethoate were28.2d,2.8d,2.3d,52.1d,2.6d and96.1d,14.2d,10.2d,41.2d,38.2d. Theobserved value of mean omethoate concertration was close to the predicted value calculated withC-t=Coeαt+C-βt1eand Ctt=Coe-α.2.2decomposition kinetics of omethoate in preserved cadaver bloodThe concentration of omethoate detected in preserved cadaver blood showed a descendedtrend in each condition. The content of omethoate in blood at20℃,20℃（1%NaF）,4℃,-20℃descended significantly to88.5±5.7%,39.7±0.9%,49.8±4.5%,41.6±6.6%（P﹤0.05）ofinitial concentration on8thd,6thh,13thd,18thd respectively. After stored57d at20℃,4℃and-20℃, the content of omethoate in blood descended to0.59±0.1%,20.8±3.5%,24.3±6.4%ofinitial concentration respectively. After stored by78h, omethoate has not been detected in bloodat20℃（1%NaF）.20℃,20℃（1%NaF） and-20℃blood groups fit to a one compartment open model with afirst-order kinetics and could be expressed as C-t=Coeαt, the decomposion half-lifes（t1/2α） ofomethoate were6.6d,10h and28.8d;4℃blood group fit to the two compartment open modelwith a first-order kinetics and could be expressed as Ct=Cαt-oe-+C1eβt, the fast and slowdecomposion half-lifes（t1/2αand t1/2β） of omethoate were4.7d and63.9d. 3. The decomposition kinetics in buried cadaversThe content of omethoate detected in gall showed a raised trend in59d, then a descendedtrend. There was no significantly change of concentration of omethoate in cardic blood during59d. The concentration of omethoate in other tissues showed a descended trend. After buried on120d,200d,380d, the omethoate only can bu detected in stomach.The research of different poisonous dose showed that on the89thd, omethoate have not beendetected in5LD₅₀and20LD₅₀dose groups in each tissues.On the120thd, omethoate just can bedetected in20LD₅₀dose group in stomach with different extract methord （grind methord）; Inother tissues, omethoate can not be detected.The research of different burial way showed that the concentration of omethoate detected inheart, liver, kidney, muscle of limb, breast muscle and stomach of dogs cadavers buried inwooden cases （coffins） on75thd were significantly higher than those in plastic bags and wovenbags; The concentration of omethoate detected in liver, kidney and stomach buried in plasticbags were significantly higher than those in woven bags.CONCLUSION:1. The postmortem redistribution, decomposition kinetics model of omethoate in preservedspecimens and buried cadaver of dogs have been developed, which can be applied to forensicidentification and study on forensic toxicokinetics of decomposition of omethoate poisoningdeath case.2. There were a site dependent and time dependent postmortem increase of omethoateconcentration in poisoned death dogs, and PMR occurred. Postmortem redistribution should betaken into consideration in the forensic identification of the poisoning death ofomethoate.Besides the heart blood, peripheral blood, liver, stomach content, but also the specimens such asmuscle and brain, in which concentrations of omethoate tend to be postmortemly stable, shouldbe sampled for analysis.3. In different preserved condition, omethoate can be decomposed in preserved blood, liver ofpoisoning dogs and in preserved cadaver blood. It suggests that cryopreservation andformaldehyde can slow down the decomposition of omethoate; The20℃（1%NaF） can speed upthe decomposion. On the72thh, omethoate could not be detected in preserved blood of dog at thecondition of20℃（1%NaF）, and also on the78thh, omethoate could not be detected in preservedcadaver blood. In the forensic identification of omethoate, the specimens for analysis should becollected and detected as soon as possible, otherwise, they should bu frozon or fixed in4%formaldehyde, but NaF should not be added into the fluid samples.4. The decomposion kinetics of omethoate in different preserved condition fit to the first-orderkinetics process. The common equation was Ct=Coe-αt+Ct1e-βand C-t=Coeαt, which could be used to conclude the concentrations of omethoate when the specimens were collected.5. The content of omethoate in the samples of buried dogs showed a sharp decrease trend. Onlyomethoate can be detected in stomach on120d,200d,380d after the burial; The poisonousdose can affect the decomposion of omethoate, which was related to the time limit of collectingthe samples; The bural way also affect the decomposion of omethoate, of which dogs buried inthe woven bags and in the wooden cases were the fastest and slowest.6. In the forensic identification of burial cadavers of omethoate poisoning death, we should takethe whole sitiuations into the consideration, which include buried time, poisonous dose andburied way, and so on, and combined with the administration way of poison and antemortemtreatment. Cadaver-dugging and toxic analysis should bu carried out as soon as possible. It canapproximately be estimated the omethoate concentration range in buried cadavers according tothe poision analysis and decomposion rule.