Distribution of 1,2-dichloropropane in blood and other tissues of rats after oral administration.

The present investigation was undertaken to determine the distribution of 1,2-dichloropropane (DCP) in the blood, liver, kidney, lung, and abdominal fat of rats after oral administration. Male rats were orally administered 62 or 125 mg/kg body weight doses of DCP dissolved in corn oil by gavage, and the concentrations in the blood and tissues were measured. The DCP concentration in the abdominal fat was much greater than in the blood and other tissues. Twenty-four-hr after oral administration, DCP could still be detected in the blood and abdominal fat in the 62-mg/kg group, and in the blood, liver, kidney, lung, and abdominal fat in the 125-mg/kg group. Our results are valuable data pertaining to the pharmacokinetics of DCP and to human health risk assessment of oral exposure to DCP.

Is it worth carrying out determination of N-butane in postmortem samples? A case report and a comprehensive review of the literature.

The aim of this article is to illustrate the importance of N-butane determination in postmortem samples through a case report and to propose actions and precautions to be taken into consideration when butane is suspected to be involved in cases of death. The case concerns a 15-year-old boy found dead after sniffing a cigarette lighter refill. Toxicological investigation revealed the presence of butane in the heart and femoral blood (1280 and 1170 µg/L, respectively), in the gastric contents (326 µg/L), and in the liver (1010 µg/kg) and lung tissues (210 µg/kg). Propane was present only in the blood samples at concentrations tenfolds lower.Butane can be involved in three kinds of fatalities: deliberate inhalations including volatile substance abuse (VSA), involuntary exposure, and homicides. A fatal outcome of butane inhalation can be caused by asphyxia and/or cardiac arrhythmia. In the context where butane exposure is evidenced by non-toxicological investigations, the usefulness of the determination of butane in postmortem samples is often questionable. However, it is admitted that butane-related deaths are generally underreported. Several difficulties including sample handling and storage, substantial variation in tissue concentrations, and lack of a lethal threshold make the interpretation of butane results challenging. In our opinion, systematic toxicological methods should be developed in order to analyze butane, at least when it concerns a typical VSA victim, even when butane is not actually suspected to be the cause of death.

Cytochrome P450 2E1 is responsible for the initiation of 1,2-dichloropropane-induced liver damage.

1,2-Dichloropropane (1,2-DCP), a solvent, which is the main component of the cleaner used in the offset printing companies in Japan, is suspected to be the causative agent of bile duct cancer, which has been recently reported at high incidence in those offset printing workplaces. While there are some reports about the acute toxicity of 1,2-DCP, no information about its metabolism related to toxicity in animals is available. As part of our efforts toward clarifying the role of 1,2-DCP in the development of cancer, we studied the metabolic pathways and the hepatotoxic effect of 1,2-DCP in mice with or without cytochrome P450 2E1 (CYP2E1) activity. In an in vitro reaction system containing liver homogenate, 1,2-DCP was only metabolized by liver tissue of wild-type mice but not by that of cyp2e1-null mice. Furthermore, the kinetics of the solvent in mice revealed a great difference between the two genotypes; 1,2-DCP administration resulted in dose-dependent hepatic damage, as shown biochemically and pathologically, but this effect was only observed in wild-type mice. The nuclear factor κB p52 pathway was involved in the liver response to 1,2-DCP. Our results clearly indicate that the oxidative metabolism of 1,2-DCP in mice is exclusively catalyzed by CYP2E1, and this step is indispensable for the manifestation of the hepatotoxic effect of the solvent.

Inhalation exposure to 1,2-dichloropropane: Distribution of blood and tissue concentrations of 1,2-dichloropropane in rats during and after exposure.

The present investigation was undertaken to determine the distribution and accumulation of 1,2-dichloropropane (DCP) in the blood, lung, liver, kidney, and abdominal fat of rats during and after inhalation exposure. Male rats were exposed to 80 or 500 ppm (v/v) DCP vapor for 360 min and the concentrations of DCP in the blood and tissues during the inhalation exposure period and after the end of the exposure period were measured. DCP accumulation in the abdominal fat was much greater than that in the blood and other tissues. Eighteen hours after the end of inhalation exposure, DCP could still be detected in the abdominal fat in the 80-ppm group, and in the blood, liver, kidney, and abdominal fat in the 500-ppm group. Our results are valuable data pertaining to the pharmacokinetics of DCP and to human health risk assessment of exposure to DCP vapor by inhalation.

Time course of blood parameters in printing workers with cholangiocarcinoma.

OBJECTIVES: We previously reported a cluster of cholangiocarcinoma patients among proof-printing workers who were exposed to 1,2-DCP for a long term. The present study was conducted to evaluate blood parameters in these proof-printing workers during and after exposure. METHODS: Health examination records during employment and after retirement were obtained for ten cholangiocarcinoma patients to analyze their blood parameters. The patients and/or their relatives were also interviewed about lifestyle and occupational history. RESULTS: All study patients were exposed to 1,2-DCP for 6-17 years. Red blood cells, hemoglobin, hematocrit, total cholesterol, triglycerides, and fasting plasma glucose were within the standard ranges for almost all patients, but the γ-glutamyl transpeptidase (γ-GTP) levels exceeded the standard range during 1,2-DCP exposure for six patients. Two of the six patients were diagnosed with cholangiocarcinoma during 1,2-DCP exposure, and the other four patients were diagnosed 1-9 years after termination of exposure. The remaining four patients had γ-GTP levels within the standard range during 1,2-DCP exposure, but had increased γ-GTP levels thereafter, and were diagnosed with cholangiocarcinoma 4-10 years after termination of exposure. Aspartate aminotransferase and alanine aminotransferase levels started to increase following the increase in γ-GTP levels. CONCLUSIONS: Workers exposed to 1,2-DCP should be provided with periodic health examinations during and after exposure. In the examination, even small increases in γ-GTP levels should be considered a signal of early development of cholangiocarcinoma.

Discovery and optimisation of 1-hydroxyimino-3,3-diphenylpropanes, a new class of orally active GPBAR1 (TGR5) agonists.

A series of non-steroidal GPBAR1 (TGR5) agonists was developed from a hit in a high-throughput screening campaign. Lead identification efforts produced biphenyl-4-carboxylic acid derivative (R)-22, which displayed a robust secretion of PYY after oral administration in a degree that can be correlated with the unbound plasma concentration. Further optimisation work focusing on reduction of the lipophilicity provided the 1-phenylpiperidine-4-carboxylic acid derivative (R)-29 (RO5527239), which showed an improved secretion of PYY and GLP-1, translating into a significant reduction of postprandial blood glucose excursion in an oral glucose tolerance test in DIO mice.

Effect of nisoldipine and olmesartan on endothelium-dependent vasodilation in essential hypertensive patients.

AIMS: To investigate whether nisoldipine and olmesartan improve endothelial function, decrease asymmetric dimethylarginine (ADMA) and alleviate the inflammatory and oxidative process. METHODS: Fifty-five essential hypertensive patients were randomized to receive nisoldipine or olmesartan for 8 weeks according to a parallel-group, active-controlled, single blind study, and 28 matched normotensive subjects served as healthy controls. Flow-mediated dilation (FMD), and plasma levels of nitric oxide (NO), endothelin-1 (ET-1), high-sensitive C-reactive protein (hs-CRP), 8-isoprostane (also named 8-isoPGF2α), and ADMA were determined. RESULTS: At baseline, the plasma levels of ADMA, ET-1, hs-CRP, and 8-isoPGF2α were markedly higher in patients with essential hypertension than in normotensive subjects (P < 0.05). A significant positive correlation was observed between plasma levels of ET-1 and ADMA in patients with essential hypertension, but not in normotensive subjects. The NO plasma concentrations were significantly lower in patients with essential hypertension than in normotensive subjects. Furthermore, hypertensive subjects demonstrated significantly lower FMD than healthy control (P < 0.05). Nisoldipine and olmesartan significantly and similarly reduced blood pressure in patients with essential hypertension (P < 0.001). At the end of the 8-week treatment, plasma ADMA and ET-1 levels were decreased significantly (P < 0.01). FMD increased significantly in nisoldipine or olmesartan-treated patients (P < 0.05). A significant decrease in plasma hs-CRP contents was observed in patients receiving nisoldipine (P < 0.05). CONCLUSION: The findings demonstrate that nisoldipine and olmesartan both improve FMD in patients with essential hypertension. This may be associated with decreased circulating levels of CRP, ET-1, and ADMA.

Quantification of a novel natural antioxidant (UP302) in rat plasma using ultra-high performance liquid chromatography-tandem mass spectrometry.

UP302 is a novel natural antioxidant isolated from Dianella ensifolia (Liliaceae). In the investigation, a specific and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry for quantitative determination of UP302 in rat plasma was developed and validated. UP302 and the internal standard daidzein were extracted from 100 µL aliquots of rat plasma using methanol. Detection of UP302 and IS was done by tandem mass spectrometry, operating in negative ion and selected reaction monitoring acquisition mode. The precursor-product ion transitions monitored for UP302 and daidzein were m/z 301.1→135.2 and 252.9→132.0, respectively. The linearity of the method was observed within the concentration range of 5-2000 ng/mL. Intra- and inter-day assay variations were less than 15%, and the accuracy values were between 99.2% and 107.3%. The method was successfully applied to stability investigation of UP302 incubated in rat plasma at 37°C and measurement of UP302 in plasma after intravenous administration of UP302 to rats at a single dose of 5 mg/kg. Incubation stability revealed that within first one hour, UP302 was rapidly declined approximately 35% and remained stable after 4 h. Pharmacokinetic values of half-life, volume of distribution, systemic clearance and mean residence time were 0.87 ± 0.58 h, 6.90 ± 3.35 L/kg, 5.89 ± 1.21 L/h kg and 0.34 ± 0.13 h, respectively.

Dysregulation of PRMT1 and PRMT6, Type I arginine methyltransferases, is involved in various types of human cancers.

Protein arginine methylation is a novel post-translational modification regulating a diversity of cellular processes, including histone functions, but the roles of protein arginine methyltransferases (PRMTs) in human cancer are not well investigated. To address this issue, we first examined expression levels of genes belonging to the PRMT family and found significantly higher expression of PRMT1 and PRMT6, both of which are Type I PRMTs, in cancer cells of various tissues than in non-neoplastic cells. Abrogation of the expression of these genes with specific siRNAs significantly suppressed growth of bladder and lung cancer cells. Expression profile analysis using the cells transfected with the siRNAs indicated that PRMT1 and PRMT6 interplay in multiple pathways, supporting regulatory roles in the cell cycle, RNA processing and also DNA replication that are fundamentally important for cancer cell proliferation. Furthermore, we demonstrated that serum asymmetric dimethylarginine (ADMA) levels of a number of cancer cases are significantly higher than those of nontumor control cases. In summary, our results suggest that dysregulation of PRMT1 and PRMT6 can be involved in human carcinogenesis and that these Type I arginine methyltransferases are good therapeutic targets for various types of cancer.

Diabetic retinopathy is associated with elevated serum asymmetric and symmetric dimethylarginines.

OBJECTIVE: Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and l-arginine directly influence nitric oxide production. Our objective was to test whether serum ADMA, SDMA, or l-arginine levels correlate with diabetic retinopathy subtype or severity. RESEARCH DESIGN AND METHODS: A total of 162 subjects with type 1 diabetes and 343 with type 2 diabetes, of whom 329 subjects had no diabetic retinopathy, 27 had nonproliferative diabetic retinopathy (NPDR), 101 had proliferative diabetic retinopathy (PDR), and 107 had clinically significant macular edema (CSME), were recruited. Blinding diabetic retinopathy was defined as severe NPDR, PDR, or CSME. Serum ADMA, SDMA, and l-arginine concentrations were determined by mass spectroscopy. RESULTS: In multivariate analysis, blinding diabetic retinopathy, PDR, and nephropathy were associated with significantly increased serum levels of ADMA (P < 0.001), SDMA (P < 0.001), and l-arginine (P = 0.001). Elevated ADMA (P < 0.001) and SDMA (P < 0.001) were also significantly associated with CSME. CONCLUSIONS: Severe forms of diabetic retinopathy are associated with elevated serum ADMA, SDMA, and l-arginine. Further investigation is required to determine whether these findings are of clinical relevance.

A proposal for comparing methods of quantitative analysis of endogenous compounds in biological systems by using the relative lower limit of quantification (rLLOQ).

Accuracy, precision and lower limit of quantification (LLOQ) are experimentally achievable key analytical factors by which the quality of analytical methods can be ascribed and objectively evaluated. Endogenous substances (endobiotica) are physiologically present in biological fluids and tissues at varying basal concentration (C(0,Ln)). Formally, the definition of accuracy and LLOQ is same for xenobiotica and endobiotica. However, these analytical factors must be determined differently, notably by considering the C(0,Ln) value of endobiotica. Often, the impact of the endogeneity on the analytical method is underestimated. This especially applies to the LLOQ, because the LLOQ values for endobiotica are regularly not fixed measures due to the varying C(0,Ln) value in biological samples. In order to circumvent these difficulties and for a more reliable and objective evaluation and comparison of analytical methods for endobiotica, this work proposes the use of the relative lower limit of quantification, i.e., rLLOQ. The rLLOQ is defined as the percentage ratio of the LLOQ value, i.e., C(LLOQ) to C(0,Ln): rLLOQ = (C(LLOQ):C(0,Ln))x100. Thus, the rLLOQ describes that fraction of C(0,Ln) that can be still determined with acceptable values for accuracy (e.g., recovery of 100+/-20%) and precision (e.g., RSD < or = 20%) or with a total error (i.e., recovery+precision) of < or = 30%. Examples from the quantitative analysis of selected endogenous compounds by previously validated GC-MS, GC-MS/MS and LC-MS/MS methods support the appropriateness and expressiveness of the rLLOQ in the quantitative analysis of endobiotica.

The effect of plasma lipids on the pharmacokinetics of chlorpyrifos and the impact on interpretation of blood biomonitoring data.

Lipophilic molecules, like chlorpyrifos (CPF), present a special problem for interpretation of biomonitoring data because both the environmental dose of CPF and the physiological (pregnancy, diet, etc.) or pathological levels of blood lipids will affect the concentrations of CPF measured in blood. The objective of this study was to investigate the distribution of CPF between plasma and tissues when lipid levels are altered in late pregnancy. CPF was sequestered more in the low-density lipid fraction of the blood during the late stages of gestation in the rat and returned to nonpregnant patterns in the dam after birth. Plasma partitioning of CPF increased with increases in plasma lipid levels and the increased partitioning of CPF into plasma lipids resulted in less CPF in other tissue compartments. Gavage dosing with corn oil also increased plasma lipids that led to a moderate increase of CPF partitioning into the plasma. To mechanistically investigate the potential pharmacokinetic effects of blood lipid changes, an existing CPF physiologically based pharmacokinetic/pharmacodynamic model for rats and humans was modified to account for altered lipid-tissue partition coefficients and for major physiological and biochemical changes of pregnancy. The model indicated that plasma CPF levels are expected to be proportional to the well-known changes in plasma lipids during gestation. There is a rapidly growing literature on the relationship of lipid profiles with different disease conditions and on birth outcomes. Increased blood concentrations of lipophilic chemicals like CPF may point to altered lipid status, as well as possibly higher levels of exposure. Thus, proper interpretation of blood biomonitoring data of lipophilic chemicals requires a careful consideration of blood lipids.

Determination of 1-furan-2-yl-3-pyridin-2-yl-propenone, an anti-inflammatory propenone compound, by high performance liquid chromatography with ultraviolet spectrometry.

1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3) has recently been synthesized and characterized to have an anti-inflammatory activity. In the present study, pharmacokinetic parameters for FPP-3 and its metabolites were determined at the same time by using high-performance liquid chromatography-ultraviolet spectrometry. Two metabolites were detected in sera when FPP-3 was administered intravenously to male SD rats. The linearity of FPP-3, M1 (1-furan-2-yl-3-pyridin-2-yl-propan-1-one) and M2 (1-furan-2-yl-3-pyridin-2-yl-propan-1-ol) was confirmed in the concentration ranges of 0.5-20, 0.101-4.04 and 1.04-20.4 microg/ml, respectively. The lower limits of quantitation of FPP-3, M1 and M2 were 0.5, 0.1 and 1.0 microg/ml, respectively. The intra- and inter-day precision and accuracy over the concentration range of target compounds were within 13.5 and 14.2%, respectively. The half-lives of FPP-3, M1 and M2 were 16.3, 27.7 and 22.1 min, respectively.

The forensic investigation of propane gas asphyxiation.

Two unusual suicides of a 19-year-old white man and a 47-year-old white man, involving propane inhalation and plastic bag suffocation, are described. The special characteristics of propane gas as an asphyxiant agent are discussed, as well as its effect on the human body. The discussion emphasizes the postmortem examination and the collection of samples for toxicologic analysis.

Quantitative determination of n-propane, iso-butane, and n-butane by headspace GC-MS in intoxications by inhalation of lighter fluid.

This report describes a fully elaborated and validated method for quantitation of the hydrocarbons n-propane, iso-butane, and n-butane in blood samples. The newly developed analytical procedure is suitable for both emergency cases and forensic medicine investigations. Its practical applicability is illustrated with a forensic blood sample after acute inhalative intoxication with lighter fluid; case history and toxicological findings are included. Identification and quantitation of the analytes were performed using static headspace extraction combined with gas chromatography-mass spectrometry. In order to reconcile the large gas volumes injected (0.5 mL) with the narrowbore capillary column and thus achieve preconcentration, cold trapping on a Tenax sorbent followed by flash desorption was applied. Adequate retention and separation were achieved isothermally at 35 degrees C on a thick-film capillary column. Sample preparation was kept to a strict minimum and involved simply adding 2.5 microL of a liquid solution of 1,1,2-trichlorotrifluoroethane in t-butyl-methylether as an internal standard to aliquots of blood in a capped vial. Standards were created by volumetric dilution departing from a gravimetrically prepared calibration gas mixture composed of 0.3% of n-propane, 0.7% of iso-butane, and 0.8% of n-butane in nitrogen. In the forensic blood sample, the following concentrations were measured: 90.0 microg/L for n-propane, 246 microg/L for iso-butane, and 846 microg/L for n-butane.

Liquefied petroleum gas (LPG) poisoning: report of two cases and review of the literature.

Two autopsy cases of men who died while connecting a liquefied petroleum gas (LPG) pipe are reported. Their blood concentrations of propane (the main content of LPG) were 0.12 and 3.40 mg/100 g, respectively. The cause of death after exposure of LPG has generally been considered to be asphyxia from hypoxia. The large differences in the blood propane levels found here and reported in the literature, however, suggest that direct toxic effects of propane poisoning may be the cause of death in some cases. Propane concentrations and the cause of death are reviewed and discussed.

Fate of dipropyl sulphide and dipropyl sulphoxide in rat.

1. Dipropyl [35S]-sulphide and dipropyl [35S]-sulphoxide were administered by gavage (4.24 mM/4 ml/kg body wt) to adult male Wistar rats following an overnight fast. 2. Urine was the major route of excretion for both compounds, with more radioactivity appearing during the second day (c. 43%) than the first (c. 26%). Only small amounts were found in the faeces (c. 5%). Biliary excretion played an important role with substantial amounts of the dose (c. 25%) passing through the bile duct during 0-48 h. Following ingestion of the sulphide large quantities of radioactivity (18%) were detected in exhaled air. Near total recoveries were achieved for both compounds, although 13% of the radioactivity remained within the carcass 3 days after administration of the sulphoxide. 3. Absorption and elimination half-lives were in the region of 5 and 8 h, respectively, for both compounds, with the sulphoxide plasma profile showing a prolonged plateau region. 4. Metabolism was limited to oxidation of the sulphur with the formation of the sulphoxide and sulphone, and trace amounts of inorganic sulphate.

Toxicological investigation of liquid petroleum gas explosion: human model for propane/ethyl mercaptan exposures.

Four individuals died as the result of a propane explosion. As with many propane explosions, the question was raised as to the adequacy of the product's odorization after the autopsy studies had been conducted. In most cases, this question leads to litigation. Ethyl mercaptan is a widely used odorant for propane and was used in this instance. Three of the four victims had blood available at autopsy for study. Quantitative analyses of the victims' blood, obtained during autopsy, were performed using gas chromatography/mass spectrometry, without subjecting the samples to hydrolysis. These analyses determined the relative amounts of propane and ethyl mercaptan in the blood to be 90, 63, and 175 mL/m3 headspace, and 0.36, 0.34, and 0.77 microgram/L blood, respectively. Since mercaptans have been reported in human blood as products of metabolism, modeling studies were conducted to establish the validity of the autopsy data and to develop an autopsy toxicology protocol for investigating explosion deaths. When subjects were not exposed to an atmosphere containing ethyl mercaptan, dimethylsulfide was the only mercaptan detectable in their blood without severe hydrolysis prior to analysis. Metabolic ethyl mercaptan is sufficiently bound to be undetectable by the methods used without hydrolysis. Human subjects were exposed to a flammable mixture of air and propane odorized with ethyl mercaptan. The analyses of the blood from these subjects produced results which were comparable with those for the explosion victims, establishing that the question of odorant adequacy can be addressed at the autopsy of propane explosion victims. It is extremely important that the pathologist and toxicologist investigating gas explosion deaths recognize the valuable evidence existing in the victim's blood.

1,2-Dichloropropane hepatotoxicity in rats after inhalation exposure.

The hepatic effects of 1,2-dichloropropane (DCP) were investigated in male Wistar rats exposed to 15, 50, 100, 250, 450, 1000, 1300, 1800 or 4900 mg DCP m-3. At the end of a 4-h period of exposure, average blood DCP levels were 0.025 and 5.38 micrograms ml-1 in animals treated with 15 and 1300 mg m-3, respectively. Blood DCP concentrations were correlated with the air DCP concentrations in the inhalation chamber. At DCP concentrations of 100 mg m-3 or higher, the liver non-protein thiol (NPT) content was significantly reduced. Assays performed 20 h after 4-h DCP exposure showed that exposure to 100-1000 mg DCP m-3 had no effect on hepatic NPT levels. The NPT content increased only in the liver of rats exposed to higher (1300-4900 mg m-3) DCP concentrations. Treatment with DCP did not cause hepatic lipid peroxidation and did not modify total protein content. The observed changes in liver cell thiol homeostasis are likely to reflect the action of reactive intermediates formed during DCP metabolism. These changes can occur in rats following exposure to considerably low levels of DCP vapour.