Law J S, Henkin R I
Res Commun Chem Pathol Pharmacol. 1984 Mar;43(3):449-62.
Thyroid hormone inhibited purified taste bud membrane adenosine 3'5'-monophosphate (cAMP) phosphodiesterase (PDE) activity in a dose-dependent manner. Taste bud membrane cAMP PDE was inhibited most effectively by thyroxine (T4) followed in order by triiodothyionine (T3), diiodotyrosine (DIT) and monoiodotyrosine (MIT). Concentrations required for 50% inhibition (IC50) of enzyme activity were about 1 x 10(-6), 1 x 10(-5), 6 x 10(-4) M and greater than 1 x 10(-3) M for T4, T3, DIT and MIT, respectively. Addition of zinc at physiological concentrations found in serum greatly augmented the inhibitory effects of T4 and T3 at lower concentrations (10(-7) and 10(-6) M, respectively) resulting in further inhibition of cAMP PDE by 40-50%. Inhibition of cAMP PDE by T4 appears to be relatively tissue selective as indicated by the IC50 of 1 x 10(-6) M for the taste bud but only 7 x 10(-6) M, 3 x 10(-5) M, and 4 x 10(-5) M, for heart, kidney and brain cAMP PDE, respectively. Inhibition of taste bud membrane cAMP PDE by T4 was competitive with substrate cAMP with a Ki of 4 microM. These results suggest that inhibition of cAMP PDE, which increases taste bud membrane intracellular cAMP, may participate in the action of thyroid hormone in the taste process.
甲状腺激素以剂量依赖的方式抑制纯化的味蕾膜腺苷3',5'-环磷酸（cAMP）磷酸二酯酶（PDE）的活性。味蕾膜cAMP PDE受甲状腺素（T4）抑制最为有效，其次依次为三碘甲状腺原氨酸（T3）、二碘酪氨酸（DIT）和一碘酪氨酸（MIT）。T4、T3、DIT和MIT对该酶活性50%抑制（IC50）所需的浓度分别约为1×10⁻⁶、1×10⁻⁵、6×10⁻⁴M和大于1×10⁻³M。添加血清中生理浓度的锌可在较低浓度（分别为10⁻⁷和10⁻⁶M）时极大增强T4和T3的抑制作用，导致cAMP PDE进一步被抑制40 - 50%。T4对cAMP PDE的抑制似乎具有相对的组织选择性，味蕾的IC50为1×10⁻⁶M，而心脏、肾脏和脑cAMP PDE的IC50分别仅为7×10⁻⁶M、3×10⁻⁵M和4×10⁻⁵M。T4对味蕾膜cAMP PDE的抑制与底物cAMP具有竞争性，Ki为4μM。这些结果表明，抑制cAMP PDE（其可增加味蕾膜细胞内cAMP）可能参与甲状腺激素在味觉过程中的作用。
