| OBJECTIVE:1. To establish the postmortem redistribution single-body animal models of methamidophos and phorate in dogs by an intragastric administration.2. To investigate the postmortem redistribution of methamidophos and phorate in dogs and provide a scientific evidence for the forensic identification of methamidophos or phorate poisoning death.METHODS:1. Study on postmortem redistribution of methamidophos in dogs. Four dogs were randomly allocated to postmortem redistribution group (n=3) and control group (n=1). The postmortem redistribution group dogs were given an intragastric administration of methamidophos with a dose 7.4mg/kg weight. As soon as the vital signs disappeared, the dogs were preserved at room temperature, and the samples such as heart blood, peripheral blood, brain, liver and right hindlimb muscle were collected at Oh,2h,4h,8h,12h,24h,48h,72h,96h,120h and 144h after the death, in which the concentration of methamidophos was detected qualitatively and quantitative by GC/MS and GC/FPD (the method 3). The control dog was given the same volume of physiological saline by the intragastric administration as the postmortem redistribution group dogs were, who was executed and the heart blood,peripheral blood, brain, liver and right hindlimb muscle were collected as the control samples in the analysis.2. Study on postmortem redistribution of phorate in dogs. Four dogs were randomly allocated to postmortem redistribution group (n=3) and control group (n=1). The postmortem redistribution group dogs were given an intragastric administration of methamidophos with a dose 0.7mg/kg weight. As soon as the vital signs disappeared, the dogs were preserved at room temperature, and the samples such as heart blood, peripheral blood, brain, liver and right hindlimb muscle were collected at Oh,2h,4h,8h,12h,24h,48h,72h and 96h after the death, in which the concentration of phorate was detected qualitatively and quantitative by GC/MS and GC/FPD (the method 3). The control dog was given the same volume of physiological saline by the intragastric administration as the postmortem redistribution group dogs were, who was executed and the heart blood, brain, liver and right hindlimb muscle were collected as the control samples in the analysis.3. Extraction and analysis. The samples were extracted by Methylene chloride. Analysis was performed with a GC equipped with a FPD and a GC/MS. The qualitative analysis was based on retention time of methamidophos and phorate in the chromatographic system coupled with the ion fragmentation spectrum in the mass spectrometer. The quantitative analysis was based on an internal standard method.4. Statistics. Data was expressed as mean±SD model and analyzed statistically with SPSS 11.5 software by t-test.RESMLTS:1. Symptoms Some toxic symptoms, such as a vomit, salivate, secretion increase, muscle thrill, decreased corneal reflex, fecal incontinence and spasm were observed in PMR gro up dogs at 28.0±2.5min after the intragastric administration of methamidophos, and the d ogs died at 75min.These symptoms observed in PMR group dogs at 17.0±2.8min after th e intragastric administration of phorate, and the dogs died at 30min.But there were nothi ng observed in control group.2. GC-FPD and GC/MS analysis2.1 In GC/MS analysis, the mornitoring ions (m/z) of mathamidophos were 126,111 and 94. In the GC-FPD analysis, the retention time of mathamidophos and tributyl phosphate (internal standard) were 4.681 min and 7.239min. The regression equation, linear range and the LOQ for determination of mathamidophos in liver and blood by GC-FPD are Yblood=0.0347X+0.0184, 0.8-64μg/mL, 0.1μg/mL and Yliver=0.0422X-0.0202,0.8-64.0μg/g,0.1μg/g.2.2 In GC/MS analysis, the mornitoring ions (m/z) of phorate were 231,121,97 and 75. In the GC-FPD analysis, the retention times of phorate and tributyl phosphate (internal st andard) were 8.037min and 7.349min.The regression equation, linear range and the LOQ for determination of phorate in liver and blood by GC-FPD are Yblood=0.6374X-0.0705, 0.1-10μg/mL, 0.01μg/mL and Yliver=0.8178X-0.1448,0.1-10.0μg/g,0.012μg/g.3. Postmortem redistribution3.1 The postmortem redistribution of mathamidophos when the dogs died, the concentration of mathamidophos detected in heart blood was significantly higher than in femoral blood, the heart blood/femoral blood contration ratios averaged 1.77. Compared with the concentration at the death, the heart blood contrcentration of mathamidophos showed a significant increase during 8h-144h after the death (P<0.05), the postmortem/death heart blood contration ratios averaged 1.81～2.09; The liver contrcentration of mathamidophos showed a significant increase at 24h after the death (P<0.05), the postmortem/death liver blood contration ratios averaged 1.81～2.09; The brain contrcentration of mathamidophos showed a significant increase at 8h-48h after the death (P<0.05), the postmortem/death liver brain contration ratios averaged 1.23～1.54. The muscle contrcentration of mathamidophos did not show the significant increase.3.2 The postmortem redistribution of phorate when the dogs died, the concentration of phorate detected in heart blood was significantly higher than in femoral blood, the heart blood/femoral blood contration ratios averaged 1.24. Compared with the concentration at the death, the heart blood contrcentration of significant showed a significant increase during 12h-24h after the death (P<0.05), the postmortem/death heart blood contration ratios averaged 1.23～1.34; The liver contrcentration of significant showed a significant increase at 24h-144h after the death (P<0.05), the postmortem/death liver blood contration ratios averaged 1.27～1.44; The brain contrcentration and the muscle contrcentration of phorate did not show the significant increase.CONCLUSION:1. The intragastric administration single-body animal model of methamidophos and phorat e for PMR has been established, which can be applied to the forensitoxicokinetics study of methamidophos and phorate poisoning death.2. For poisoned death dogs after a dose of 8LD50 methamidophos,the heart/femoral and the postmortem/death blood contration ratios of methamidophos averaged 1.77 and 1.81～2.09; The postmortem/death liver and brain contration ratios averaged 1.81～2.09 and 1.23～1.54, the concentration of methamidophos in the muscle changed insignificantly. These indicate that there were a position dependent blood methamidophos concentration and time dependent postmortem increase of blood, liver, brain methamidophos concentration increase in poisoned death dogs, and PMR occurred. The methamidophos concentration in muscle was less affected by PMR.3. For poisoned death dogs after a dose of 4OLD50 phorate, the heart/femoral and the postmortem /death blood contration ratios of phorate averaged 1.24 and 1.23～1.34; The postmortem/death liver and brain contration ratios averaged 1.27～1.44; The concentration of phorate in the muscle changed insignificantly. These indicate that there were a position dependent blood phorate concentration and time dependent postmortem increase of blood, liver phorate concentration increase in poisoned death dogs, and PMR occurred. The phorate concentrations in muscle and brain were less affected by PMR.4. There are postmortem redistribution of methamidophos and phorate in poisoning death dogs. Postmortem redistribution should be taken into consideration in the forensic identif ication of the poisoning death of methamidophos and phorate.Besides the heart blood, per ipheral blood, liver, stomach content, but also the specimen such as muscle and brain, in which concentrations of methamidophos and phorate tend to be postmortemly stable, sho uld be sampled for analysis. |
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