Kurl R N, Abraham M, Olnes M J
Program in Clinical Pharmacology, Brown University School of Medicine, Providence, RI 02912.
Toxicology. 1993 Jan 29;77(1-2):103-14. doi: 10.1016/0300-483x(93)90141-e.
TCDD is known to induce thymic atrophy in several mammalian species through activation of programmed cell death, or apoptosis. To investigate the time course of events which precede TCDD-induced thymic apoptosis in vitro, experiments were performed with thymocytes isolated from immature rats. Peak accumulation of both total and specifically bound [3H]TCDD was observed at 60 min post incubation. Incubation of cells with 10 nM TCDD resulted in significant increases in RNA polymerase activity and incorporation of [3H]uridine at 30 min, indicating increased RNA synthesis in response to TCDD. TCDD-induced stimulation of [3H]uridine incorporation was not significantly altered in the presence of cycloheximide, while this effect was abrogated in the presence of actinomycin D. Incubation of thymocytes with 10 nM TCDD also stimulated the activity of poly(A)polymerase, the enzyme catalyzing mRNA polyadenylation, at time points beyond 30 min. No significant increases in [35S] incorporation were observed in cells treated with 10 nM TCDD, although analysis of detergent and high salt extracted nuclear proteins by SDS-PAGE and coomassie blue staining revealed the increased abundance of at least two proteins with molecular masses of 52,000 and 42,000 Da, respectively. These studies reveal that thymocyte nuclei rapidly accumulated TCDD in vitro, leading to increased RNA synthesis, poly(A)polymerase activity and protein synthesis. These events correlate closely with the process of programmed cell death.
已知2,3,7,8-四氯二苯并对二恶英（TCDD）可通过激活程序性细胞死亡或凋亡，在几种哺乳动物物种中诱导胸腺萎缩。为了研究体外TCDD诱导胸腺细胞凋亡之前的事件时间进程，使用从未成熟大鼠分离的胸腺细胞进行了实验。孵育60分钟后观察到总[3H]TCDD和特异性结合的[3H]TCDD的峰值积累。用10 nM TCDD孵育细胞导致30分钟时RNA聚合酶活性和[3H]尿苷掺入量显著增加，表明对TCDD的反应中RNA合成增加。在放线菌酮存在下，TCDD诱导的[3H]尿苷掺入刺激没有显著改变，而在放线菌素D存在下这种作用被消除。用10 nM TCDD孵育胸腺细胞在30分钟后的时间点也刺激了聚（A）聚合酶的活性，该酶催化mRNA聚腺苷酸化。在用10 nM TCDD处理的细胞中未观察到[35S]掺入的显著增加，尽管通过SDS-PAGE和考马斯亮蓝染色对去污剂和高盐提取的核蛋白进行分析显示，至少两种分子量分别为52,000和42,000 Da的蛋白质丰度增加。这些研究表明，胸腺细胞核在体外迅速积累TCDD，导致RNA合成、聚（A）聚合酶活性和蛋白质合成增加。这些事件与程序性细胞死亡过程密切相关。
