Estrogenic activity and metabolism of n-butyl benzyl phthalate in vitro: identification of the active molecule(s).
Some phthalates are suspected to disrupt the endocrine system, especially by mimicking estrogens. N-butyl benzyl phthalate (BBP) has estrogenic effects in vitro but not in vivo. The aim of this study was to identify the active molecule(s) (parent compound and/or metabolite(s)) involved in the estrogenic activities of BBP. The estrogenic effects of BBP and its in vivo metabolites were assessed using the following tests: E-Screen, ER binding, and PR induction tests on the human breast cancer cell line MCF-7 (ER(+)). BBP, the parent compound, was a partial agonist. It stimulated MCF-7 proliferation in the E-Screen assay and increased cytosolic progesterone receptors (PR) levels in a concentration-dependent manner. No BBP metabolites were active except hippuric acid (HA), which had a weak effect at very high concentrations. BBP and HA stimulatory effects on MCF-7 proliferation were antagonized by tamoxifen. However, no competition was observed between BBP or HA and 17beta-estradiol for binding to the estrogen receptor (ER). BBP metabolism by MCF-7 cells was also investigated. After a 48-h incubation, only 10% of the initial BBP remained in the culture medium, demonstrating that BBP was extensively metabolized by the MCF-7 cells. The radioactivity recovered in the medium was represented by: mono-n-butyl phthalate (MBuP, 25%) and mono-n-benzyl phthalate (MBeP, 48%), phthalic acid (6%), and benzoic acid (3%). Since none of these metabolites had estrogenic activities, this study demonstrates that the parent compound was the active molecule involved in the in vitro estrogenic effects of BBP.
Picard
K
K
Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, laboratoire de Toxicologie, 1 Esplanade Erasme, Dijon 21000, France.
Lhuguenot
J C
JC
Lavier-Canivenc
M C
MC
Chagnon
M C
MC
D001667:Binding, Competitive; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism / Q000633:toxicity; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D004968:Estrogens, Non-Steroidal / Q000378:metabolism* / Q000633:toxicity*; D008401:Gas Chromatography-Mass Spectrometry; D006626:Hippurates / Q000494:pharmacology; D006801:Humans; D018716:Molecular Mimicry; D010795:Phthalic Acids / Q000378:metabolism* / Q000633:toxicity*; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000096:biosynthesis; D013629:Tamoxifen / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D020847:Estrogen Receptor Modulators; D004968:Estrogens, Non-Steroidal; D006626:Hippurates; D010795:Phthalic Acids; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen; D004958:Estradiol; C030514:hippuric acid; C027561:butylbenzyl phthalate