Single ingestion of di-(2-propylheptyl) phthalate (DPHP) by male volunteers: DPHP in blood and its metabolites in blood and urine.

Di-(2-propylheptyl) phthalate (DPHP) is used as a plasticizer for polyvinyl chloride products. A tolerable daily intake of DPHP of 0.2 mg/kg body weight has been derived from rat data. Because toxicokinetic data of DPHP in humans were not available, it was the aim of the present work to monitor DPHP and selected metabolites in blood and urine of 6 male volunteers over time following ingestion of a single DPHP dose (0.7 mg/kg body weight). Concentration-time courses in blood were obtained up to 24 h for DPHP, mono-(2-propylheptyl) phthalate (MPHP), mono-(2-propyl-6-hydroxyheptyl) phthalate (OH-MPHP), and mono-(2-propyl-6-oxoheptyl) phthalate (oxo-MPHP); amounts excreted in urine were determined up to 46 h for MPHP, OH-MPHP, oxo-MPHP, and mono-(2-propyl-6-carboxyhexyl) phthalate (cx-MPHP). All curves were characterized by an invasion and an elimination phase the kinetic parameters of which were determined together with the areas under the concentration-time curves in blood (AUCs). AUCs were: DPHP > MPHP > oxo-MPHP > OH-MPHP. The amounts excreted in urine were: oxo-MPHP > OH-MPHP> > cx-MPHP > MPHP. The AUCs of MPHP, oxo-MPHP, or OH-MPHP could be estimated well from the cumulative amounts of urinary OH-MPHP or oxo-MPHP excreted within 22 h after DPHP intake. Not considering possible differences in species-sensitivity towards unconjugated DPHP metabolites, it was concluded from a comparison of their AUCs in DPHP-exposed humans with corresponding earlier data in rats that there is no increased risk of adverse effects associated with the internal exposure of unconjugated DPHP metabolites in humans as compared to rats when receiving the same dose of DPHP per kg body weight.

Urinary excretion of heptanones, heptanoles and 2,5-heptanedione after controlled acute exposure of volunteers to n-heptane.

A lack of well-established parameters and assessment values currently impairs biomonitoring of n-heptane exposure. Using controlled inhalation experiments, we collected information on urinary n-heptane metabolite concentrations and the time course of metabolite excretion. Relationships between external and internal exposure were analysed to investigate the suitability of selected metabolites to reflect n-heptane uptake. Twenty healthy, non-smoking males (aged 19-38 years, median 25.5) were exposed for 3 h to 167, 333 and 500 ppm n-heptane, each. Spot urine samples of the volunteers, collected before exposure and during the following 24 h, were analysed for heptane-2-one, 3-one, 4-one, 2,5-dione, 1-ol, 2-ol, 3-ol, and 4-ol using headspace solid phase dynamic extraction gas chromatography/mass spectrometry (HS-SPDE-GC/MS). Starting from median pre-exposure concentrations between <0.5 (3-one) and 82.9 µg/L (4-one), exposure increased the concentrations for all parameters except for 4-one. Median post-exposure concentrations ranged up to 840.4 µg/L (2-ol) and decreased with half-lifes <3 h after exposure. Non-parametric correlation analyses (n = 47, p < 0.05) revealed weak to moderate associations of volume related metabolite excretion with external exposure for 2-one, 3-one and 2,5-dione (R = 0.332-0.753). Heptanol excretion was moderately associated with exposure (R ≥ 0.509) only after creatinine adjustment. Lacking association with external exposure impedes the use of 4-one as heptane biomarker, whereas 2-ol and 3-ol turned out to be sensitive indicators of exposure if creatinine correction is applied. By providing fundamental data on a panel of eight potential heptane metabolites, our study can help to promote biological monitoring of n-heptane exposure.

Determination of tuaminoheptane in doping control urine samples.

Since January 2007, the list of prohibited substances established by the World Anti-Doping Agency includes the sympathomimetic compound tuaminoheptane (1-methyl-hexylamine, 2-heptylamine). Primarily used as nasal decongestant drug it has been considered relevant for sports drug testing due to its stimulating properties. A confirmatory gas chromatographic-mass spectrometric procedure was developed including liquid-liquid extraction and imine formation of tuaminoheptane employing various aldehydes and ketones such as formaldehyde, acetaldehyde, benzaldehyde and acetone. Extraction and derivatisation conditions were optimised for utmost efficiency, and characteristic fragment ions obtained after electron ionisation allowed for a sensitive and selective analytical assay, which was validated with regard to recovery (50%), lower limit of detection (20 ng mL(-1)) as well as interday- and intraday precision (<15%). The applicability to authentic urine samples was demonstrated using administration study specimens obtained from two male persons using Rhinofluimucil (tuaminoheptane hemisulfate) for intranasal application. The administered drug was detected up to 46 h after repeated topical instillation of a total of approximately 3 mg.

Identification of the n-heptane metabolites in rat and human urine.

Numerous n-heptane metabolites have been identified and quantified by gas chromatography and mass spectrometry in some tissues and in the urine of Sprague Dawley rats exposed for 6 h to 1800 ppm n-heptane. 2-Heptanol and 3-heptanol were the main biotransformation products of the solvent. 2-Heptanone, 3-heptanone, 4-heptanol, 2,5-heptanedione, gamma-valerolactone, 2-ethyl-5-methyl-2,3-dihydrofuran and 2,6-dimethyl-2,5-dihydropyran were also found as metabolites of n-heptane. In five shoe factory workers and in three rubber factory workers the mean exposure to technical heptane was measured (n-heptane ranged between 5 and 196 mg/m3). In the urine collected at the end of their work shift some n-heptane biotransformation products were found: 2-heptanol, 3-heptanol, 2-heptanone, 4-heptanone and 2,5-heptanedione. 2-Heptanol was the main n-heptane metabolite and its urinary concentrations ranged between 0.1 and 1.9 mg/l. Urinary 2,5-heptanedione was detectable only in some samples and at very low concentration (0.1-0.4 mg/l). These data suggest that n-heptane can be considered as a neurotoxic product, since it gives rise to 2,5-heptanedione, but the small amount of the urinary metabolite is very unlikely to cause clinical damage to the peripheral nervous system.

Identification of volatile metabolites of inhaled n-heptane in rat urine.

Alkanes, alcohols, and ketones which are metabolized to a gamma-diketone can produce peripheral neuropathy in experimental animals and in man. A study was conducted to obtain information about the metabolic pathway of n-heptane and its potential neurotoxicity. Female Wistar rats were exposed to 2000 ppm n-heptane inhalation for 12 weeks. Metabolites in urine were identified by gas chromatography-mass spectrometry. Urinary metabolites were quantified following 6-hr n-heptane exposures. n-Heptane metabolites were 1-, 2-, 3-, and 4-heptanols, 2- and 3-heptanones, 2,5- and 2,6-heptanediols, 5-hydroxy-2-heptanone, 6-hydroxy-2-heptanone, 6-hydroxy-3-heptanone, 2,5- and 2,6-heptanediones, and gamma-valerolactone. The amount of urinary metabolites increased greatly after the second exposure day, achieving a steady-state concentration on subsequent exposure days over the 12 weeks of the exposure regimen. These results showed that n-heptane was metabolized mainly by hydroxylation at omega- 1 carbon atom and to a lesser extent at the omega- 2 carbon atom. 2-Heptanol, 6-hydroxy-2-heptanone, and 3-heptanol were the major metabolites and were excreted as sulfates and glucuronides. 2,5-Heptanedione, which is a neurotoxic agent, was the metabolite found in least amounts (2.4 +/- 2 micrograms/rat) in the urine. No clinical evidence of neurotoxicity was observed after n-heptane exposure. Apparently, the lack of neurotoxicity was due to a low production of 2,5-heptanedione, the toxic metabolite.