Morishige W K, Joun N S
Endocrinology. 1982 Nov;111(5):1587-94. doi: 10.1210/endo-111-5-1587.
Between the 4th and 10th days of postnatal life in the rat, serum corticosterone levels were low and basal, while the rate of [3H]thymidine incorporation into lung DNA was maximal. From day 13, serum corticosterone levels began to rise significantly, and the lung [3H]thymidine incorporation rate began to fall dramatically; however, these events were obtunded by propylthiouracil-induced hypothyroidism. When 6- to 8-day-old euthyroid pups were given a single sc injection of 10 micrograms dexamethasone, the rate of DNA synthesis in the lung fell by 96.7% of the initial rate at 24 h. This steroidal effect was blunted in hypothyroid pups and restored by exogenous thyroid hormone. The thyroid status of the pup did not modify the response patterns of lung phosphodiesterase and cytosolic glucocorticoid receptor levels to dexamethasone treatment, although both parameters were influenced by thyroid hormone availability. Radiocholine incorporation into lung phospholipids, which was altered in hypothyroidism, was unaffected by dexamethasone treatment. An in vivo assessment of radiothymidine incorporation into DNA of various tissues in 5-day-old euthyroid pups given 10 micrograms dexamethasone 24 h earlier revealed that of the several tissues in which inhibition of DNA synthesis was demonstrable, the developing lung was the most sensitive to the anti-mitogenic steroidal effect. When considered in the light of existing evidence, these observations suggest that glucocorticoids play an important role in triggering lung cytodifferentiation during the third postnatal week in the rat, and that preconditioning of the lung by thyroid hormone optimizes this developmental effect of glucocorticoids.
在大鼠出生后的第4天至第10天，血清皮质酮水平较低且处于基础状态，而[3H]胸腺嘧啶核苷掺入肺DNA的速率则达到最大值。从第13天开始，血清皮质酮水平开始显著上升，肺[3H]胸腺嘧啶核苷掺入率开始急剧下降；然而，丙硫氧嘧啶诱导的甲状腺功能减退症会减弱这些变化。当给6至8日龄的甲状腺功能正常的幼鼠单次皮下注射10微克地塞米松时，24小时后肺中DNA合成速率下降至初始速率的96.7%。这种类固醇效应在甲状腺功能减退的幼鼠中减弱，并可通过外源性甲状腺激素恢复。幼鼠的甲状腺状态并未改变肺磷酸二酯酶和胞质糖皮质激素受体水平对地塞米松治疗的反应模式，尽管这两个参数均受甲状腺激素可利用性的影响。地塞米松治疗并未影响甲状腺功能减退时肺磷脂中放射性胆碱的掺入，而甲状腺功能减退时肺磷脂中放射性胆碱的掺入发生了改变。对24小时前给予10微克地塞米松的5日龄甲状腺功能正常的幼鼠体内各种组织DNA中放射性胸腺嘧啶核苷掺入情况的评估显示，在可证明DNA合成受到抑制的几种组织中，发育中的肺对类固醇抗有丝分裂效应最为敏感。根据现有证据来看，这些观察结果表明，糖皮质激素在大鼠出生后第三周触发肺细胞分化过程中起重要作用，并且甲状腺激素对肺的预处理可优化糖皮质激素的这种发育效应。
