Incerpi Sandra, De Vito Paolo, Luly Paolo, Spagnuolo Silvana, Leoni Silvia
Department of Biology, University of Rome Roma Tre, Viale Marconi 446, 00146 Rome, Italy.
Endocrinology. 2002 May;143(5):1660-8. doi: 10.1210/endo.143.5.8767.
Rapid nongenomic effects of thyroid hormones L-T(3) and L-T(4) on two plasma membrane transport systems were investigated in 14-d-old and 19-d-old chick embryo hepatocytes. The Na(+)/H(+) exchanger activity was measured using the intracellular pH-sensitive fluorescent probe 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester, whereas the amino acid transport was estimated by [1-(14)C]-2-aminoisobutyric acid uptake. System A amino acid transport activation was linear to hormone concentration, whereas the Na/H exchanger gave a bell-shaped dose-response curve, with a maximum at the physiological hormone concentration of 1 nM. The specificity of the effect was verified by the use of inhibitors and analogues. The thyroid hormone analog 3,5-diiodo-L-thyronine was able to mimic some of the hormone effects, but with a lower efficiency. The effect on the Na(+)/H(+) exchanger was identified for 14-d-old and 19-d-old cells, whereas the amino acid transport could only be activated at the late stage of embryo development. Both transport systems were activated through a signal transduction pathway involving PKC, MAPK pathway, and PI3K, even though the differences in response behavior indicate a differential modulation of the two transport systems by L-T(3) and L-T(4). These results clearly demonstrate the existence of rapid nongenomic action of thyroid hormones also in avian cells, and show that activation of System A amino acid transport is not directly correlated to changes in intracellular pH. For the first time, evidence is presented which suggests that short-term effects of thyroid hormones may play a role during fetal development and cell differentiation.
研究了甲状腺激素L-T3和L-T4对14日龄和19日龄鸡胚肝细胞两种质膜转运系统的快速非基因组效应。使用细胞内pH敏感荧光探针2',7'-双-(2-羧乙基)-5-(和-6)-羧基荧光素乙酰甲酯测量Na+/H+交换器活性，而通过[1-(14)C]-2-氨基异丁酸摄取估计氨基酸转运。系统A氨基酸转运激活与激素浓度呈线性关系，而Na/H交换器给出钟形剂量反应曲线，在1 nM的生理激素浓度下达到最大值。通过使用抑制剂和类似物验证了效应的特异性。甲状腺激素类似物3,5-二碘-L-甲状腺原氨酸能够模拟一些激素效应，但效率较低。对14日龄和19日龄细胞确定了对Na+/H+交换器的效应，而氨基酸转运仅在胚胎发育后期被激活。尽管反应行为的差异表明L-T3和L-T4对两种转运系统的调节不同，但两种转运系统均通过涉及PKC、MAPK途径和PI3K的信号转导途径被激活。这些结果清楚地证明了甲状腺激素在禽类细胞中也存在快速非基因组作用，并表明系统A氨基酸转运的激活与细胞内pH的变化没有直接关系。首次提出证据表明甲状腺激素的短期效应可能在胎儿发育和细胞分化过程中起作用。
