Comparative disposition of dimethylaminoethanol and choline in rats and mice following oral or intravenous administration.

Dimethylaminoethanol (DMAE) and its salts have been used to treat numerous disorders in humans and hence safety of its use is a concern. DMAE is a close structural analog of choline, an essential nutrient. Exposure to DMAE may affect choline uptake and synthesis. The current investigation characterizes: 1) the absorption, distribution, metabolism, and excretion (ADME) of DMAE in Wistar Han rats and B6C3F1 mice following a single gavage or intravenous (IV) administration of 10, 100 or 500 mg/kg [14C]DMAE, and 2) the ADME of [14C]choline (160 mg/kg) and the effect on its disposition following pre-treatment with DMAE (100 or 500 mg/kg). In both rats and mice, following gavage administration, DMAE was excreted in urine (16-69%) and as exhaled CO2 (3-22%). The tissue retention was moderate (21-44%); however, the brain concentrations were low and there was no accumulation. Serum choline levels were not elevated following administration of DMAE. The DMAE metabolites in urine were DMAE N-oxide and N,N-dimethylglycine; the carcinogen, N-N-dimethylnitrosamine, was not detected. The pattern of disposition of [14C]choline following gavage administration was similar to that of [14C]DMAE. Prior treatment with DMAE had minimal effects on choline disposition. The pattern of disposition of [14C]DMAE and [14C]choline following IV administration was similar to gavage administration. There were minimal dose-, sex- or species-related effects following gavage or IV administration of [14C]DMAE or [14C]choline. Data from the current study did not support previous reports that: 1) DMAE alters choline uptake and distribution, or 2) that DMAE is converted into choline in vivo.

Towards point of care testing for C. difficile infection by volatile profiling, using the combination of a short multi-capillary gas chromatography column with metal oxide sensor detection.

Rapid volatile profiling of stool sample headspace was achieved using a combination of short multi-capillary chromatography column (SMCC), highly sensitive heated metal oxide semiconductor (MOS) sensor and artificial neural network (ANN) software. For direct analysis of biological samples this prototype offers alternatives to conventional GC detectors and electronic nose technology. The performance was compared to an identical instrument incorporating a long single capillary column (LSCC). The ability of the prototypes to separate complex mixtures was assessed using gas standards and homogenised in house 'standard' stool samples, with both capable of detecting more than 24 peaks per sample. The elution time was considerably faster with the SMCC resulting in a run time of 10 minutes compared to 30 minutes for the LSCC. The diagnostic potential of the prototypes was assessed using 50 C. difficile positive and 50 negative samples. The prototypes demonstrated similar capability of discriminating between positive and negative samples with sensitivity and specificity of 85% and 80% respectively. C. difficile is an important cause of hospital acquired diarrhoea, with significant morbidity and mortality around the world. A device capable of rapidly diagnosing the disease at the point of care would reduce cases, deaths and financial burden.

A pilot study of faecal volatile organic compounds in faeces from cholera patients in Bangladesh to determine their utility in disease diagnosis.

The aim of this pilot study was to analyse the volatile organic compounds in faecal samples collected from cholera patients in Bangladesh to determine biomarkers that could be used for disease diagnosis. Samples were collected from patients at the International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh and also from healthy controls at the same institution. The volatile organic compounds were extracted from the headspace above the sample using solid phase microextraction and analysed using gas chromatography-mass spectrometry. A biomarker was identified in the cholera samples that could be used for disease diagnosis.

Estrogenic phenol and catechol metabolites of PCBs modulate catechol-O-methyltransferase expression via the estrogen receptor: potential contribution to cancer risk.

Commercial PCB mixtures have been shown to induce liver tumors in female rats and this effect has been attributed to the effects of PCBs on estrogen metabolism. Catechol metabolites of PCBs are potent inhibitors of COMT activity and are likely to contribute significantly to reduced clearance of genotoxic catechol metabolites of estrogen. The effect of PCB metabolites on COMT expression in cultured cells was investigated to explore potential mechanisms by which PCB exposure alters catechol estrogen clearance. We hypothesize that estrogenic PCB metabolites may contribute to reduction of COMT expression via interaction with the estrogen receptor. To test this hypothesis, human MCF-7 cells were exposed to PCB analogues and the expression of COMT determined. Western blot analysis demonstrated that COMT protein levels were statistically significantly reduced by both the phenolic and the catechol compounds, an effect which was abolished by the anti-estrogen, ICI182780. The above suggests that COMT levels may be reduced by estrogenic PCB metabolites, via interactions between PCB metabolites and the ER. It supports the hypothesis that both phenolic and catechol metabolites of PCBs may contribute to PCB-mediated carcinogenesis through reduction of COMT levels and activities and subsequent reduction in clearance of endogenous and xenobiotic catechols.

An analysis of volatiles in the headspace of the faeces of neonates.

A gas chromatography/mass spectrometry (GCMS) analysis of the headspace from the faeces of neonates was undertaken to record the volatiles associated with preterm babies on a neonatal unit. The compounds ethanol, acetone, 2-ethyl-1-hexanol, 3-methylbutanal, hexanal and 2,3-butanedione occurred with the highest frequency. The volatiles analysed were then compared to a previously published study of the volatiles from asymptomatic adult faeces. Fewer compounds were found in the neonatal faeces and virtually no sulfides were detected, in contrast to the adult samples where carbon disulfide, dimethyl disulfide and dimethyl sulfide were ubiquitous. In addition, 7 of the most abundant 15 volatile compounds were found to be aldehydes, while in contrast only 2, acetaldehyde and benzaldehyde, were present in the most abundant 15 compounds found in the headspace of adult faeces. 2-Ethyl-1-hexanol was considerably more abundant in the neonate stool compared to adult stool, and probably reflects high exposure to plastic materials containing plasticizers. The potential of disease diagnoses from the analysis of volatiles emitted from neonate faeces is discussed.

Metabolism and disposition of 1-bromopropane in rats and mice following inhalation or intravenous administration.

Workplace exposure to 1-bromopropane (1-BrP) can potentially occur during its use in spray adhesives, fats, waxes, and resins. 1-BrP may be used to replace ozone depleting solvents, resulting in an increase in its annual production in the US, which currently exceeds 1 million pounds. The potential for human exposure to 1-BrP and the reports of adverse effects associated with potential occupational exposure to high levels of 1-BrP have increased the need for the development of biomarkers of exposure and an improved understanding of 1-BrP metabolism and disposition. In this study, the factors influencing the disposition and biotransformation of 1-BrP were examined in male F344 rats and B6C3F1 mice following inhalation exposure (800 ppm) or intravenous administration (5, 20, and 100 mg/kg). [1,2,3-(13)C]1-BrP and [1-(14)C]1-BrP were administered to enable characterization of urinary metabolites using NMR spectroscopy, LC-MS/MS, and HPLC coupled radiochromatography. Exhaled breath volatile organic chemicals (VOC), exhaled CO(2), urine, feces, and tissues were collected for up to 48 h post-administration for determination of radioactivity distribution. Rats and mice exhaled a majority of the administered dose as either VOC (40-72%) or (14)CO(2) (10-30%). For rats, but not mice, the percentage of the dose exhaled as VOC increased between the mid ( approximately 50%) and high ( approximately 71%) dose groups; while the percentage of the dose exhaled as (14)CO(2) decreased (19 to 10%). The molar ratio of exhaled (14)CO(2) to total released bromide, which decreased as dose increased, demonstrated that the proportion of 1-BrP metabolized via oxidation relative to pathways dependent on glutathione conjugation is inversely proportional to dose in the rat. [(14)C]1-BrP equivalents were recovered in urine (13-17%, rats; 14-23% mice), feces (<2%), or retained in the tissues and carcass (<6%) of rats and mice administered i.v. 5 to 100 mg/kg [(14)C]1-BrP. Metabolites characterized in urine of rats and mice include N-acetyl-S-propylcysteine, N-acetyl-3-(propylsulfinyl)alanine, N-acetyl-S-(2-hydroxypropyl)cysteine, 1-bromo-2-hydroxypropane-O-glucuronide, N-acetyl-S-(2-oxopropyl)cysteine, and N-acetyl-3-[(2-oxopropyl)sulfinyl]alanine. These metabolites may be formed following oxidation of 1-bromopropane to 1-bromo-2-propanol and bromoacetone and following subsequent glutathione conjugation with either of these compounds. Rats pretreated with 1-aminobenzotriazole (ABT), a potent inhibitor of P450 excreted less in urine (down 30%), exhaled as (14)CO2 (down 80%), or retained in liver (down 90%), with a concomitant increase in radioactivity expired as VOC (up 52%). Following ABT pretreatment, rat urinary metabolites were reduced in number from 10 to 1, N-acetyl-S-propylcysteine, which accounted for >90% of the total urinary radioactivity in ABT pretreated rats. Together, these data demonstrate a role for cytochrome P450 and glutathione in the dose-dependent metabolism and disposition of 1-BrP in the rat.

Catechol metabolites of polychlorinated biphenyls inhibit the catechol-O-methyltransferase-mediated metabolism of catechol estrogens.

The catechol metabolites of estradiol, 2- and 4-hydroxyestradiol (2-OHE(2) and 4-OHE(2), respectively) are potent signaling molecules and are hypothesized to be central to estrogen-linked carcinogenesis. Methylation by catechol-O-methyltransferase (COMT) is the principal means of catechol estrogen (CE) deactivation in the liver and other tissues. The present studies were conducted to determine the effects of PCBs and catechol metabolites of PCBs on the COMT-mediated catabolism of 4-OHE(2) and 2-OHE(2) in vitro and in vivo. Liver homogenates of female Sprague-Dawley rats treated with Aroclor 1254 for 21 days (5 mg/kg/day) showed a 30 and 40% reduction of COMT activity toward 2-OHE(2) and 4-OHE(2), respectively. Incubation of [(3)H]-beta-estradiol with these same liver homogenates, followed by HPLC analysis, demonstrated an elevation of CEs and a nearly complete reduction in levels of methylated catechol estrogens. In classical enzyme kinetics studies, COMT was demonstrated to have a high affinity for catechol PCBs, with K(m)'s approximately equivalent to those of CEs. Catechol PCBs were also potent inhibitors of CE O-methylation. These data suggest that PCBs may significantly alter the metabolism of catechol estrogens in vivo and that this effect may be mediated by catechol metabolites of PCBs. It is further speculated that methyltransferase inhibition by PCB catechols may contribute to PCB-mediated endocrine effects and liver carcinogenesis.

Phenolphthalein metabolite inhibits catechol-O-methyltransferase-mediated metabolism of catechol estrogens: a possible mechanism for carcinogenicity.

Phenolphthalein (PT), used in over-the-counter laxatives, has recently been identified as a multisite carcinogen in rodents, but the molecular species responsible for the carcinogenicity is not known. A catechol metabolite of PT, hydroxyphenolphthalein (PT-CAT), was recently identified and may be the molecular species responsible for at least part of the toxicity/carcinogenicity of PT. We hypothesize that PT-CAT inhibits the enzyme catechol-O-methyltransferase (COMT) and therefore potentiates genotoxicity by either PT-CAT itself or the endogenous catechol estrogens (CEs) in susceptible tissues. The present studies were conducted to determine the effects of PT treatment and PT-CAT itself on the COMT-mediated metabolism of 4- and 2-hydroxyestradiol both in vitro and in vivo. Female mice were treated with PT (50 mg/kg/d) for 21 days and then euthanized. PT-CAT concentration in urine reached plateau levels by 7 days of exposure. An O-methylated metabolite of PT-CAT was detected in feces. In vitro experiments demonstrated that PT treatment resulted in an increase in free CEs, which are normally cleared by COMT and a concurrent decrease in the capacity of hepatic catechol clearance by COMT. In vitro, PT-CAT was a substrate of COMT, with kinetic properties within the range measured with endogenous substrates. PT-CAT was an extremely potent mixed-type inhibitor of the O-methylation of the catechol estrogens, with 90-300 nM IC50s. The above data, when taken together, suggest that chronic administration of PT may enhance metabolic redox cycling of both PT-CAT and the catechol estrogens and this, in turn, may contribute to PT-induced tumorigenesis.

In vitro estrogenicity of the catechol metabolites of selected polychlorinated biphenyls.

A considerable body of work has demonstrated that phenolic polychlorinated biphenyl (PCB) metabolites, structural analogues to estradiol, bind to the soluble estrogen receptor (ER) and that hydroxy PCB-ER complexes will translocate into the nucleus and bind to ER response elements in cultured cells. Although catechol estrogens exhibit weak estrogenic activity, the catechol PCB metabolites which are structurally similar to these ER agonists have gone untested for potential estrogenicity. In the present work we have assessed the estrogenicity of this second group of PCB metabolites, the catechols. The test compounds used in the present study were chosen to elucidate the effects of chlorine and catechol position on in vitro estrogenicity. Cultured HeLa cells, transfected with the estrogen reporter gene ERET81CAT and mouse ER cDNA, were incubated with PCB catechols. The cells were harvested at 28 h posttransfection and assayed for chloramphenicol acetyl transferase (CAT) activity. The responses elicited by the PCB catechols tested fell within the range of effect measured for the catechol estrogens and phenolic PCBs, and were within the range previously reported for other "environmental estrogens" such as nonylphenol and o,p'-DDT. Maximal measured responses were achieved at concentrations approximately two to three orders of magnitude higher than that of 17-beta-estradiol, indicating that PCB catechols have estrogenic activity in vitro. The extent of chlorination and the position of the catechol (3,4 vs 2,3 substitution) were important in determining estrogenicity in the compounds tested. The 2,3-catechol showed no detectable activity in this system, while activity of the 3, 4-catechols increased with the degree of chlorination. The observed estrogenicity of PCB catechols suggests that further oxidative metabolism of estrogenic PCB phenolic metabolites would not necessarily result in lowering the total estrogenic burden of a PCB-exposed organism. The present results imply that if estrogenic activity is assigned to an individual phenol, the potential contribution of its catechol metabolites to the total estrogenic burden should also be taken into consideration.

The effect of chlorine substitution on the dermal absorption of polychlorinated biphenyls.

The fate of selected mono-, di-, tetra-, and hexachlorobiphenyls was investigated following single dermal administration (0.4 mg/kg) to determine the effects of chlorine substitution on the dermal absorption and disposition of polychlorinated biphenyls (PCBs). Single dermal doses of 14C-labeled mono-, di-, tetra-, and hexachlorobiphenyls were administered to 1-cm2 areas on the backs of F-344 male rats. Unabsorbed radioactivity was removed from the dose site either at euthanasia or 48 h postdose. Distribution of radioactivity in the dose site and selected tissues was determined by serial sacrifice at time points up to 2 weeks. Dermal penetration varied inversely with degree of chlorination and at 48 h ranged from ca. 100% for monochlorobiphenyl to ca. 30% for the hexachlorobiphenyl. Penetration rate constants correlated well with log kow. PCBs were retained in the epidermis for up to 2 weeks postdose. The data from these studies suggest that systemic absorption of PCBs involves a combination of sequential processes including penetration across the stratum corneum, possibly metabolism in the epidermis and/or dermis, adsorption to proteins, and finally absorption into the systemic circulation. The skin favors the rapid absorption of less chlorinated PCBs, but the relatively rapid metabolism and elimination of these compounds would result in lower body burdens. More highly chlorinated PCBs penetrate less rapidly but remain in the site of exposure and slowly enter the systemic circulation. The dermal absorption of a commercial PCB mixture was modeled, and the results suggest that the net result of the differences in absorbance rates would be a greater body burden of higher chlorinated PCBs relative to those that have a lower chlorine content.

Diethanolamine absorption, metabolism and disposition in rat and mouse following oral, intravenous and dermal administration.

1. The disposition of [14C]diethanolamine (DEA) (1) was determined in rat after oral, i.v. and dermal administration, and in mouse after dermal administration. 2. Oral administration of DEA to rat was by gavage of 7 mg/kg doses once and after daily repeat dosing for up to 8 weeks. Oral doses were well absorbed but excreted very slowly. DEA accumulated to high concentrations in certain tissues, particularly liver and kidney. The steady-state of bioaccumulation was approached only after several weeks of repeat oral dosing, and the half-life of elimination was approximately 1 week. 3. DEA was slowly absorbed through the skin of rat (3-16% in 48 h) after application of 2-28 mg/kg doses. Dermal doses ranging from 8 to 80 mg/kg were more readily absorbed through mouse skin (25-60%) in 48 h of exposure, with the percent of the applied dose absorbed increasing with dose. 4. Single doses (oral or i.v.) of DEA were excreted slowly in urine (c. 22-25% in 48 h) predominantly as the parent compound. There was minimal conversion to CO2 or volatile metabolites in breath. The profile of metabolites appearing in urine changed after several weeks of repeat oral administration, with significant amounts of N-methylDEA and more cationic metabolites appearing along with unchanged DEA.

The influence of cytochrome P450 enzyme activity on the composition and quantity of volatile organics in expired breath.

Abstract We have previously described a method to capture, identify and quantify volatile components in expired breath. The purpose of this research is to provide a non-invasive means to measure biomarkers of metabolism in vivo. In the present studies, the effect of 1-aminobenzotriazole (ABT), an inhibitor of diverse cytochrome P450 (P450) enzymes, on the composition of volatile organic chemicals (VOCs) expired in the breath of male F-344 rats was determined in parallel with the catalytic activities and total content of hepatic P450. lntraperitoneal administration of ABT (100 mg kg-(1)) to rats resulted in markedly diminished hepatic microsomal P450 content and activities. The extent of inhibition was near maximal at 4 h, at which time approximately 50% of the total P450 content, about 65% of the CYPlA2 activity, 55% of the CYP2E1 activity, and about 80% of CYP2B activity were lost. Inhibition was maintained to 48 h post-dosing, but P450 content and activities had largely been restored by day 7. Concomitant with the inhibition of P450 were corresponding increases (up to several hundred-fold) in the molar amount of volatiles appearing in the breath of ABT-treated animals, and the rebound of P450 levels was attended by corresponding decreases in the appearance of breath volatiles. These studies indicate that P450 plays a major role in the metabolism of VOCs appearing in breath, and that these chemicals can serve as markers on P450 activity in vivo.

Metabolism, bioaccumulation, and incorporation of diethanolamine into phospholipids.

Diethanolamine (DEA) is a major industrial chemical which has low acute toxicity, but, on repeat exposure, has significant cumulative toxicity. The present work suggests that the cumulative toxicity can be attributed to the fact that, unlike most small polar molecules, DEA accumulates to high concentrations in certain tissues following repeat exposure. The highest concentrations of DEA were seen in liver, kidney, spleen, and brain. Investigations described here have determined that DEA is metabolized by biosynthetic routes common to ethanolamine and is conserved, O-phosphorylated, N-methylated, and incorporated into phosphoglyceride and sphingomyelin analogues as the parent compound and as its N-methyl and N,N-dimethyl derivatives. This is the first report of the conjugation of a xenobiotic headgroup with a natural ceramide to form aberrant sphingomyelins. DEA-derived phosphoglycerides constituted the majority of aberrant phospholipid following acute administration. On repeat administration, DEA bioaccumulated to plateau levels at approximately 8 weeks. This bioaccumulation was accompanied by an increasing degree of methylation and accumulation of aberrant sphingomylenoid lipids in tissues. Uptake and incorporation of DEA into ceramide derivatives in human liver slices were also demonstrated in the present studies. It is speculated that the cumulative toxicity observed on repeat administration of DEA to rats is caused in part by increasing levels of aberrant phospholipids derived from this unnatural alkanolamine.