Arem R, Chayoth R, Shenkenberg T, Field J B
Arch Biochem Biophys. 1984 Apr;230(1):168-77. doi: 10.1016/0003-9861(84)90098-5.
Incubation of dog thyroid slices with 1 microM acetylcholine (ACH) for 3 h followed by a second 2-h incubation without it induces a diminution of stimulation of glucose oxidation by ACH during a third incubation of 45 min. Using a calcium-free medium during all incubations prevents the desensitization and reduces, but does not abolish, ACH stimulation of glucose oxidation. EGTA [ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid] (2 mM) added to the calcium-free medium in all incubations prevents both refractoriness and stimulation of glucose oxidation induced by ACH. Calcium depletion during the first incubation only, achieved by using EGTA and a calcium-free medium, also prevents refractoriness but not the augmentation of glucose oxidation caused by ACH. Incubation of thyroid slices with 1 microM ionophore A23817 during the 3-h first incubation decreases the stimulation of glucose oxidation induced by its readdition or by 1 microM ACH added for the first time in the third incubation. Ionophore-induced desensitization is not related to a cholinergic muscarinic receptor effect. Initial incubation of dog thyroid slices with 1 microM ACH diminishes the subsequent stimulation of glucose oxidation by 0.5 microM ionophore. However, the ACH-induced desensitization to ionophore can be overcome by a 10-fold increase in the amount of ionophore in the third incubation. Ionophore (1 microM) in the first incubation also induces refractoriness to thyroid-stimulating hormone (TSH) (10 mU/ml)-stimulated glucose oxidation in the third incubation. In contrast, initial incubation of thyroid slices with TSH (25 mU/ml) does not affect the stimulation of glucose oxidation by 0.5 microM ionophore added during the third incubation. These results suggest that increased intracellular calcium plays a major role in, or even mediates, ACH-induced desensitization in the thyroid gland.
将犬甲状腺切片与1微摩尔乙酰胆碱（ACH）一起孵育3小时，随后在无ACH的情况下再孵育2小时，这会导致在第三次45分钟的孵育过程中，ACH对葡萄糖氧化的刺激作用减弱。在所有孵育过程中使用无钙培养基可防止脱敏现象，并减少但不会消除ACH对葡萄糖氧化的刺激。在所有孵育过程中，向无钙培养基中添加2毫摩尔乙二醇双（β-氨基乙基醚）-N，N'-四乙酸（EGTA）可防止ACH诱导的不应性以及葡萄糖氧化的刺激。仅在第一次孵育期间通过使用EGTA和无钙培养基实现的钙耗竭，也可防止不应性，但不会阻止ACH引起的葡萄糖氧化增加。在第一次3小时孵育期间，将甲状腺切片与1微摩尔离子载体A23817一起孵育，会降低其重新添加或在第三次孵育中首次添加1微摩尔ACH所诱导的葡萄糖氧化刺激。离子载体诱导的脱敏与胆碱能毒蕈碱受体效应无关。犬甲状腺切片最初与1微摩尔ACH孵育会减少随后0.5微摩尔离子载体对葡萄糖氧化的刺激。然而，第三次孵育中离子载体量增加10倍可克服ACH诱导的对离子载体的脱敏。第一次孵育中的离子载体（1微摩尔）还会在第三次孵育中诱导对促甲状腺激素（TSH）（10毫单位/毫升）刺激的葡萄糖氧化产生不应性。相反，甲状腺切片最初与TSH（25毫单位/毫升）孵育不会影响第三次孵育期间添加的0.5微摩尔离子载体对葡萄糖氧化的刺激。这些结果表明，细胞内钙增加在甲状腺中ACH诱导的脱敏中起主要作用，甚至可能介导该过程。
