Carvalho D P, Dupuy C, Gorin Y, Legue O, Pommier J, Haye B, Virion A
Institut National de la Sante et de la Recherche Medicale, Le Kremlin-Bicetre Cedex, France.
Endocrinology. 1996 Mar;137(3):1007-12. doi: 10.1210/endo.137.3.8603567.
Hydrogen peroxide (H2O2) is an essential electron acceptor for thyroid peroxidase-catalyzed iodination and coupling reactions. In the presence of iodide, its production is a limiting step in thyroid hormone biosynthesis. Several studies have demonstrated that the thyroid particulate fraction contains a Ca2+- and NADPH- dependent H@O@ generator (NADPH-O2:oxidoreductase), the so- called thyroid NADPH-oxidase. It has recently been demonstrated that cellular H2O2 release is under the tonic control of TSH in primary cultures of dog thyrocytes. The present study evaluates the effect of TSH on the thyroid NADPH-oxidase and cytochrome c reductase activities, two enzymes believed to be involved on H2O2 generation in the thyroid gland. There was almost no detectable NADPH-dependent H2O2 generator in the membranes of cells grown for 18 h without TSH. But cells grown in the presence of TSH (0.1 mU/ml) had a CA2+- and NADPH-dependent H2O2-generating activity that increased up to the third day in culture, as did the cell iodide organification capacity. This increase was also partially blocked by 12-O-tetradecanoylphorbol 13-acetate and cycloheximide. Forskolin and 8-bromo-cAMP both reproduced the action of TSH on the Ca2+- and NADPH-dependent H2O2 generator. In contrast, the thyroid NADPH-cytochrome c reductase activity in particles from control cells was similar to that of TSH-treated cells and was unaffected by forskolin or 12-O-tetradecanoylphorbol 13-acetate. These results suggest that NADPH-cytochrome c reductase activity is not regulated by TSH and, thus, reinforce the idea that this enzyme is not involved in thyroid H2O2 generation. On the other hand, the Ca2+- and NADPH-dependent H2O2 generator, so-called thyroid NADPH- oxidase, is induced by TSH through the cAMP cascade. Thus, it seems to be another marker of thyroid differentiation, in addition to thyroperoxidase and thyroglobulin, and could play a key role in thyroid hormone production.
过氧化氢（H2O2）是甲状腺过氧化物酶催化碘化和偶联反应中必不可少的电子受体。在碘化物存在的情况下，其生成是甲状腺激素生物合成中的一个限制步骤。多项研究表明，甲状腺微粒部分含有一种依赖Ca2+和NADPH的H2O2生成器（NADPH-O2：氧化还原酶），即所谓的甲状腺NADPH氧化酶。最近已证明，在犬甲状腺细胞原代培养物中，细胞H2O2释放受促甲状腺激素（TSH）的紧张性控制。本研究评估了TSH对甲状腺NADPH氧化酶和细胞色素c还原酶活性的影响，这两种酶被认为参与甲状腺中H2O2的生成。在无TSH的情况下培养18小时的细胞的膜中几乎检测不到依赖NADPH的H2O2生成器。但是在TSH（0.1 mU/ml）存在下培养的细胞具有一种依赖Ca2+和NADPH的H2O2生成活性，该活性在培养的第三天之前一直增加，细胞碘有机化能力也是如此。这种增加也被12-O-十四烷酰佛波醇13-乙酸酯和放线菌酮部分阻断。福斯高林和8-溴-cAMP均重现了TSH对依赖Ca2+和NADPH的H2O2生成器的作用。相反，对照细胞颗粒中的甲状腺NADPH-细胞色素c还原酶活性与TSH处理的细胞相似，并且不受福斯高林或12-O-十四烷酰佛波醇13-乙酸酯的影响。这些结果表明，NADPH-细胞色素c还原酶活性不受TSH调节，因此，强化了这种酶不参与甲状腺H2O2生成的观点。另一方面，依赖Ca2+和NADPH的H2O2生成器，即所谓的甲状腺NADPH氧化酶，由TSH通过cAMP级联反应诱导产生。因此，除了甲状腺过氧化物酶和甲状腺球蛋白外，它似乎是甲状腺分化的另一个标志物，并且可能在甲状腺激素产生中起关键作用。
