Urinary biomarkers of di-isononyl phthalate in rats.
Commercial di-isononyl phthalate (DiNP) is a mixture of various branched-chain dialkyl phthalates mainly containing nine-carbon alkyl isomers. At high doses in rodents, DiNP is a carcinogen, and a developmental toxicant. After exposure, the diester isomers are de-esterified to form hydrolytic monoesters, monoisononyl phthalates (MiNP), which subsequently metabolize to form oxidative metabolites. These metabolites can be excreted in urine or feces. The urinary excretion of DiNP metabolites was monitored in adult female Sprague-Dawley rats after oral administration of a single dose (300 mg/kg) of commercial DiNP. The metabolites were extracted from urine, resolved with high performance liquid chromatography, analyzed by mass spectrometry, and tentatively identified based on their chromatographic separation and mass spectrometric fragmentation pattern. Because DiNP is an isomeric mixture, its metabolites were also isomeric mixtures that eluted from the HPLC column with close retention times. Mono(carboxy-isooctyl)phthalate (MCiOP) was identified as the major metabolite of DiNP; in addition, mono(hydroxy-isononyl)phthalate (MHiNP) and mono(oxo-isononyl)phthalate (MOiNP) were present. Furthermore, metabolites of di-isooctyl phthalate (DiOP) and di-isodecyl phthalate (DiDP) were also detected. Excretion toxicokinetics of the DiNP metabolites in urine followed a biphasic pattern with initial rapid decay in concentration. Despite potential differences in the metabolism of DiNP among species, MCiOP, MHiNP and MOiNP were detected in humans with no known exposure to DiNP at levels significantly higher than MiNP suggesting that these oxidative metabolites may be better urinary biomarkers of human exposure to DiNP than is MiNP.
Silva
Manori J
MJ
Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA. zca2@cdc.gov
Kato
Kayoko
K
Wolf
Cynthia
C
Samandar
Ella
E
Silva
Sathya S
SS
Gray
Earl L
EL
Needham
Larry L
LL
Calafat
Antonia M
AM
D000284:Administration, Oral; D000818:Animals; D015415:Biomarkers / Q000737:chemistry / Q000652:urine; D005260:Female; D006801:Humans; D008658:Inactivation, Metabolic; D015394:Molecular Structure; D010795:Phthalic Acids / Q000737:chemistry / Q000652:urine*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization
D015415:Biomarkers; D010795:Phthalic Acids; C573544:mono(carboxy-isooctyl)phthalate; C012125:diisononyl phthalate