Alvarez L, Hernández S, Martinez-de-Mena R, Kolliker-Frers R, Obregón M J, Kleiman de Pisarev D L
Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires 1121, Argentina.
Toxicology. 2005 Feb 28;207(3):349-62. doi: 10.1016/j.tox.2004.10.006.
Treatment of male Wistar rats with hexachlorobenzene (HCB) (1000 mg/kg b.w.) for 3-30 days decreases circulating levels of thyroxine (T4) but does not affect triiodothyronine (T3). Time courses were determined for 5' deiodinase type I (5' D-I) activity in thyroid, liver, and kidney and 5' deiodinase type II (5' D-II) activity in brown adipose tissue (BAT) to test the possibility that increased deiodinase activity might contribute to the maintenance of the serum T3 level. Specific 5' D-I activity was increased in the thyroid at 21 days and thereafter. No significant changes were observed in the liver, however, total 5' D-I activity in this tissue was increased at 30 days of treatment as a consequence of liver weight enhancement. HCB decreased kidney 5' D-I activity after 15 days, and BAT 5' D-II activity after 21 days of treatment. Total body 5' D-I activity was significantly increased by 30 days of HCB-treatment. HCB increased the activity of hepatic T4 uridine diphosphoglucuronosyl transferase (UDPGT) in a time-dependent manner, without changes in T3 UDPGT. We propose that increased T4 to T3 conversion in the thyroid and in the greatly enlarged liver may account for the maintenance of serum T3 concentration in hypothyroxinemic HCB-treated rats.
用六氯苯（HCB）（1000毫克/千克体重）对雄性Wistar大鼠进行3至30天的处理后，甲状腺素（T4）的循环水平降低，但三碘甲状腺原氨酸（T3）不受影响。测定了甲状腺、肝脏和肾脏中I型5'脱碘酶（5'D-I）活性以及棕色脂肪组织（BAT）中II型5'脱碘酶（5'D-II）活性的时间进程，以检验脱碘酶活性增加可能有助于维持血清T3水平的可能性。在21天及之后，甲状腺中的特异性5'D-I活性增加。肝脏中未观察到显著变化，然而，由于肝脏重量增加，该组织中的总5'D-I活性在处理30天时增加。HCB处理15天后降低了肾脏5'D-I活性，处理21天后降低了BAT 5'D-II活性。HCB处理30天后，全身5'D-I活性显著增加。HCB以时间依赖性方式增加了肝脏T4尿苷二磷酸葡萄糖醛酸基转移酶（UDPGT）的活性，而T3 UDPGT没有变化。我们认为，甲状腺和大幅增大的肝脏中T4向T3转化的增加可能是HCB处理的甲状腺功能减退大鼠血清T3浓度维持的原因。
