PT - JOURNAL ARTICLE AU - Yoshihisa Kato AU - Koichi Haraguchi AU - Tomoaki Yamazaki AU - Ryohei Kimura AU - Nobuyuki Koga AU - Shizuo Yamada AU - Masakuni Degawa TI - THE DECREASE IN LEVEL OF SERUM THYROXINE BY 2,2′,4,5,5′-PENTACHLOROBIPHENYL IN RATS AND MICE: NO CORRELATION WITH FORMATION OF METHYLSULFONYL METABOLITES AID - 10.1124/dmd.105.006189 DP - 2005 Nov 01 TA - Drug Metabolism and Disposition PG - 1661--1665 VI - 33 IP - 11 4099 - http://dmd.aspetjournals.org/content/33/11/1661.short 4100 - http://dmd.aspetjournals.org/content/33/11/1661.full SO - Drug Metab Dispos2005 Nov 01; 33 AB - A relationship between formation of methylsulfonyl (MeSO2) metabolites of 2,2′,4,5,5′-pentachlorobiphenyl (PentaCB) and decrease in serum thyroxine (T4) level was examined in the rats and mice after a single i.p. injection of PentaCB (342 μmol/kg body weight). In either rats or mice, levels of the 3- and 4-MeSO2 metabolites of PentaCB in the liver and feces increased in a time-dependent fashion up to 8 days after PentaCB-treatment. However, there was a marked difference between rats and mice in the amount of the metabolites formed, and the cumulative amount of the either MeSO2 metabolite for 8 days after PentaCB treatment in the liver was 4 to 15 times higher in mice than in rats. On the other hand, a 40 to 60% decrease in level of serum total T4 occurred in both rats and mice at 1 day after PentaCB treatment, and the decrease was retained up to 8 days after PentaCB treatment. Thus, there was a marked difference between rats and mice in the formation of MeSO2 metabolites from PentaCB but not a significant difference between rats and mice in PentaCB-induced decrease in the level of serum total T4, indicating that PentaCB-induced decrease in the level of serum total T4 is not necessarily dependent on the MeSO2 metabolites formed. The American Society for Pharmacology and Experimental Therapeutics