Effects of methoxychlor and its metabolite 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane on 11β-hydroxysteroid dehydrogenase activities in vitro

Methoxychlor (MXC) is primarily used as a pesticide and widely present in the environment. The objective of the present study is to investigate the direct effects of MXC and its metabolite 2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE) on two isoforms of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1 and 11 beta-HSD2) in vitro. Human liver microsome, rat testis microsome and adult Leydig cells were used for the measurement of 11 beta-HSD1 activity. Human placental and rat kidney microsomes were used for 11 beta-HSD2 activity. The IC50 values on human 11 beta-HSD1 by MXC and HPTE were 1.91 +/- 0.07 and 8.88 +/- 0.08 mu M, respectively. HPTE inhibited rat 11 beta-HSD1 with IC50 of 9.15 +/- 0.05 mu M, while MXC did not inhibit the enzyme. MXC and HPTE were competitive inhibitors of 11 beta-HSD1. HPTE also inhibited human and rat 11 beta-HSD2 with IC50 values of 55.57 +/- 0.08 and 12.96 +/- 0.11 mu M, respectively, while MXC did not inhibit 11 beta-HSD2. In summary, our results showed that MXC and its metabolite HPTE inhibited both isoforms of 11 beta-HSD in a species-and chemical structure-dependent manner. (C) 2013 Elsevier Ireland Ltd. All rights reserved.