Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-2 (of 2 Records) |
Query Trace: Preau Jr JL[original query] |
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Urinary and serum metabolites of di-n-pentyl phthalate in rats
Silva MJ , Furr J , Samandar E , Preau Jr JL , Gray LE , Needham LL , Calafat AM . Chemosphere 2010 82 (3) 431-6 Di-n-pentyl phthalate (DPP) is used mainly as a plasticizer in nitrocellulose. At high doses, DPP acts as a potent testicular toxicant in rats. We administered a single oral dose of 500mgkg(-1)bw of DPP to adult female Sprague-Dawley rats (N=9) and collected 24-h urine samples 1d before and 24- and 48-h after DPP was administered to tentatively identify DPP metabolites that could be used as exposure biomarkers. At necrosis, 48h after dosing, we also collected serum. The metabolites were extracted from urine or serum, resolved with high performance liquid chromatography, and detected by mass spectrometry. Two DPP metabolites, phthalic acid (PA) and mono(3-carboxypropyl) phthalate (MCPP), were identified by using authentic standards, whereas mono-n-pentyl phthalate (MPP), mono(4-oxopentyl) phthalate (MOPP), mono(4-hydroxypentyl) phthalate (MHPP), mono(4-carboxybutyl) phthalate (MCBP), mono(2-carboxyethyl) phthalate (MCEP), and mono-n-pentenyl phthalate (MPeP) were identified based on their full scan mass spectrometric fragmentation pattern. The omega-1 oxidation product, MHPP, was the predominant urinary metabolite of DPP. The median urinary concentrations (mugmL(-1)) of the metabolites in the first 24h urine collection after DPP administration were 993 (MHPP), 168 (MCBP), 0.2 (MCEP), 222 (MPP), 47 (MOPP), 26 (PA), 16 (MPeP), and 9 (MCPP); the concentrations of metabolites in the second 24h urine collection after DPP administration were significantly lower than in the first collection. We identified some urinary metabolic products in the serum, but at much lower levels than in urine. Because of the similarities in metabolism of phthalates between rats and humans, based on our results and the fact that MHPP can only be formed from the metabolism of DPP, MHPP would be the most adequate DPP exposure biomarker for human exposure assessment. Nonetheless, based on the urinary levels of MHPP, our preliminary data suggest that human exposure to DPP in the United States is rather limited. |
Variability over one week in the urinary concentrations of metabolites of diethyl phthalate and di(2-Ethylhexyl) phthalate among 8 adults: an observational study
Preau Jr JL , Wong LY , Silva MJ , Needham LL , Calafat AM . Environ Health Perspect 2010 118 (12) 1748-54 BACKGROUND: Phthalates are metabolized and eliminated in urine within hours after exposure. Several reports suggest that concentrations of phthalate metabolites in a spot urine sample can provide a reliable estimation of exposure to phthalates for up to several months. OBJECTIVES: We examined inter- and intra-participant and inter- and intra-day variability in the concentrations of monoethyl phthalate (MEP), the major metabolite of diethyl phthalate, commonly used in personal care products, and mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), a polyvinyl chloride plasticizer of which diet is the principal exposure source, among eight adults who collected all urine voids (average 7.6 samples/person/day) for 1 week. METHODS: We analyzed the urine samples using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. RESULTS: Regardless of the type of void (spot, first morning, 24-hour collections), for MEP, inter-participant variability in concentrations accounted for > 75% of the total variance. By contrast, for MEHHP, within-participant variability was the main contributor (69%-83 %) of the total variance. Furthermore, we observed considerable intra-day variability in the concentrations of spot samples for MEHHP (51%) and MEP (21%). CONCLUSIONS: MEP and MEHHP urinary concentrations varied considerably during 1 week, but the main contributors to the total variance differed (inter-day variability, MEHHP; inter-participant variability, MEP) regardless of the sampling strategy (spot, first morning, 24-hour collection). The nature of the exposure (diet vs. other lifestyle factors) and timing of urine sampling to evaluate exposure to phthalates should be considered. For DEHP and phthalates to which people are mostly exposed through diet, collecting 24-hour voids for only 1 day may not be advantageous compared with multiple spot collections. When collecting multiple spot urine samples, changing the time of collection may provide the most complete approach to assess exposure to diverse phthalates. |
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