Smith T J, Kline E L
Department of Medicine, State University of New York, Buffalo.
Biochem Biophys Res Commun. 1988 Sep 30;155(3):1293-6. doi: 10.1016/s0006-291x(88)81281-6.
3,3',5-L-triiodothyronine (T3) can inhibit tyrosinase activity in B16/C3 melanoma cells in culture and block the induction of that enzyme by imidazole (Endocrinol. 119, 2118, 1986). The current study examined the effect of thyroxine (T4) on tyrosinase activity. Proliferating cultures were exposed to either T3 (0-500 nM) or T4 (0-50,000 nM) in addition to imidazole (10 mM). Imidazole induced enzyme activity by approximately 3-fold and T3 could block that induction with a maximal inhibition occurring at 10 nM. Even at the highest concentrations used, T4 had no effect on tyrosinase activity. These studies disclose that T4, the tetraiodinated parent compound from which T3 is derived, is devoid of intrinsic biological activity in this T3 responsive system.
3,3',5-L-三碘甲状腺原氨酸（T3）可抑制培养的B16/C3黑色素瘤细胞中的酪氨酸酶活性，并阻断咪唑对该酶的诱导作用（《内分泌学》119, 2118, 1986）。本研究检测了甲状腺素（T4）对酪氨酸酶活性的影响。除了加入咪唑（10 mM）外，将增殖培养物暴露于T3（0 - 500 nM）或T4（0 - 50,000 nM）中。咪唑可使酶活性诱导增加约3倍，T3可阻断该诱导作用，在10 nM时出现最大抑制。即使使用最高浓度，T4对酪氨酸酶活性也无影响。这些研究表明，T4作为T3的四碘母体化合物，在这个对T3有反应的系统中缺乏内在生物活性。
