title: Estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes.
abstract: In this study we examined estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes. Trans-1,2-diphenylcyclobutane (TCB), cis-1,2-diphenylcyclobutane (CCB), 1,3-diphenylpropane, 2,4-diphenyl-1-butene, 2,4,6-triphenyl-1-hexene, and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin were negative in the yeast estrogen screening assay and estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, TCB exhibited estrogenic activity after incubation with liver microsomes of phenobarbital-treated rats in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Minor activity was observed when liver microsomes of untreated or 3-methylcholanthrene-treated rats were used instead of those from phenobarbital-treated rats. CCB, 1,3-diphenylpropane, and 2,4-diphenyl-1-butene also exhibited estrogenic activity after metabolic activation by liver microsomes, but the activity was lower than that of TCB. 2,4,6-Triphenyl-1-hexene and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin did not show estrogenic activity after such incubation. When TCB was incubated with liver microsomes of phenobarbital-treated rats in the presence of NADPH, three metabolites were detected by high-performance liquid chromatography (HPLC). One metabolite isolated by HPLC exhibited a significant estrogenic activity. The active metabolite was identified as trans-1-(4-hydroxyphenyl)-2-phenylcyclobutane by mass and nuclear magnetic resonance spectral analysis. These results suggest that the estrogenic activity of TCB was caused by the formation of the 4-hydroxylated metabolite.
authors.affiliation: Institute of Pharmaceutical Science, Hiroshima University School of Medicine, Hiroshima, Japan. skitamu@hiroshima-u.ac.jp
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kitamura
authors.forename: Motoko
authors.initials: M
authors.lastname: Ohmegi
authors.forename: Seigo
authors.initials: S
authors.lastname: Sanoh
authors.forename: Kazumi
authors.initials: K
authors.lastname: Sugihara
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Yoshihara
authors.forename: Nariaki
authors.initials: N
authors.lastname: Fujimoto
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ohta
mesh_terms: D000818:Animals; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D004703:Endocrine System / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008862:Microsomes, Liver; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000187:drug effects / Q000502:physiology; D013343:Styrenes / Q000378:metabolism* / Q000494:pharmacology*; D015003:Yeasts
chemical_list: D011960:Receptors, Estrogen; D013343:Styrenes