title: Hepatic and intestinal glucuronidation of mono(2-ethylhexyl) phthalate, an active metabolite of di(2-ethylhexyl) phthalate, in humans, dogs, rats, and mice: an in vitro analysis using microsomal fractions.
abstract: Mono(2-ethylhexyl) phthalate (MEHP) is an active metabolite of di(2-ethylhexyl) phthalate (DEHP) and has endocrine-disrupting effects. MEHP is metabolized into glucuronide by UDP-glucuronosyltransferase (UGT) enzymes in mammals. In the present study, the hepatic and intestinal glucuronidation of MEHP in humans, dogs, rats, and mice was examined in an in vitro system using microsomal fractions. The kinetics of MEHP glucuronidation by liver microsomes followed the Michaelis-Menten model for humans and dogs, and the biphasic model for rats and mice. The K m and V max values of human liver microsomes were 110 µM and 5.8 nmol/min/mg protein, respectively. The kinetics of intestinal microsomes followed the biphasic model for humans, dogs, and mice, and the Michaelis-Menten model for rats. The K m and V max values of human intestinal microsomes were 5.6 µM and 0.40 nmol/min/mg protein, respectively, for the high-affinity phase, and 430 µM and 0.70 nmol/min/mg protein, respectively, for the low-affinity phase. The relative levels of V max estimated by Eadie-Hofstee plots were dogs (2.0) > mice (1.4) > rats (1.0) ≈ humans (1.0) for liver microsomes, and mice (8.5) > dogs (4.1) > rats (3.1) > humans (1.0) for intestinal microsomes. The percentages of the V max values of intestinal microsomes to liver microsomes were mice (120 %) > rats (57 %) > dogs (39 %) > humans (19 %). These results suggest that the metabolic abilities of UGT enzymes expressed in the liver and intestine toward MEHP markedly differed among species, and imply that these species differences are strongly associated with the toxicity of DEHP.
authors.affiliation: Department of Biochemical Toxicology, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan. nhanioka@hamayaku.ac.jp.
authors.forename: Nobumitsu
authors.initials: N
authors.lastname: Hanioka
authors.affiliation: Department of Biochemical Toxicology, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Isobe
authors.affiliation: Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kinashi
authors.affiliation: Department of Biochemical Toxicology, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Tanaka-Kagawa
authors.affiliation: Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, 468-8503, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Jinno
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D004051:Diethylhexyl Phthalate / Q000031:analogs & derivatives* / Q000378:metabolism; D004285:Dogs; D020719:Glucuronides / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D007700:Kinetics; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008861:Microsomes / Q000187:drug effects* / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D008875:Middle Aged; D015394:Molecular Structure; D051381:Rats; D013045:Species Specificity; D055815:Young Adult
chemical_list: D020719:Glucuronides; D004051:Diethylhexyl Phthalate; C016599:mono-(2-ethylhexyl)phthalate
keywords: Glucuronidation; Intestinal microsomes; Liver microsomes; Mono(2-ethylhexyl) phthalate (MEHP); UDP-glucuronosyltransferase (UGT)