Moustafa S A
Department of Zoology, Faculty of Science, Suez Canal University, Ismailia, Egypt.
Int J Toxicol. 2001 Jan-Feb;20(1):15-20. doi: 10.1080/109158101750103332.
The current study is an attempt to elucidate the link between glutathione (GSH) as a major endogenous antioxidant and the thyroid hormone levels. Rats were treated with a single intraperitoneal (IP) dose of either ZnCl2 (5 mg/kg) or allyl alcohol (AIAI) (1.5 mmol/kg), which acts as a GSH-depleting agent. ZnCl2 and AIAI were administered either alone (Zn- and AlAl-treated groups) or in combination (AIAI + Zn-treated group). Blood and liver samples were collected 5 hours post treatment in all groups. Zinc was used because of its potential intracellular regulatory effect as a calcium antagonist. The data indicate a decrease in the serum levels of triiodothyronine (T3) and thyroxin (T4), the T3/T4 ratio, and serum and liver total protein in AlAl-treated rats. Increases in the serum levels of aminotransferases, hepatic calcium, and lipid peroxidation products were observed. The decrease in T3 and the T3/T4 ratio indicates a reduced capacity of the microsomes to convert T4 into T3. Rats treated with AlAl + Zn had replenished hepatic GSH and showed a marked decrease in the serum levels of aminotransferases and in the liver calcium contents and lipid peroxidation products compared to AlAl-treated rats. In contrast, zinc treatment failed to normalize the serum levels of total protein, T3 and T4, and the T3/T4 ratio in the same rats. Rat treated with ZnCI2 alone tended to have a lower serum protein level that was accompanied with a significant decrease in both serum T3 and the T3/T4 ratio. The effect of zinc in increasing capillary permeability with the probable leakage of some serum proteins including the thyroid-binding proteins could possibly be the reason behind this finding. Possible covalent binding of AIAI metabolites to some cellular proteins may explain the persistence of reduced liver protein levels in zinc-protected rats.
本研究旨在阐明作为主要内源性抗氧化剂的谷胱甘肽（GSH）与甲状腺激素水平之间的联系。用单次腹腔注射（IP）剂量的ZnCl2（5mg/kg）或烯丙醇（AIAI）（1.5mmol/kg，一种GSH消耗剂）处理大鼠。ZnCl2和AIAI单独给药（Zn处理组和AIAI处理组）或联合给药（AIAI+Zn处理组）。所有组在处理后5小时采集血液和肝脏样本。使用锌是因为其作为钙拮抗剂具有潜在的细胞内调节作用。数据表明，AIAI处理的大鼠血清中三碘甲状腺原氨酸（T3）、甲状腺素（T4）水平、T3/T4比值以及血清和肝脏总蛋白水平降低。观察到血清转氨酶、肝脏钙和脂质过氧化产物水平升高。T3和T3/T4比值降低表明微粒体将T4转化为T3的能力下降。与AIAI处理的大鼠相比，AIAI+Zn处理的大鼠肝脏GSH得到补充，血清转氨酶水平、肝脏钙含量和脂质过氧化产物显著降低。相比之下，锌处理未能使同一大鼠的血清总蛋白、T3和T4水平以及T3/T4比值恢复正常。单独用ZnCl2处理的大鼠血清蛋白水平往往较低，同时血清T3和T3/T4比值显著降低。锌增加毛细血管通透性并可能导致包括甲状腺结合蛋白在内的一些血清蛋白渗漏，这可能是这一发现的原因。AIAI代谢产物可能与某些细胞蛋白发生共价结合，这可以解释锌保护的大鼠肝脏蛋白水平持续降低的现象。
