Ribonucleic acid synthesis during the early action of thyroid hormones.
Ribonucleic acid synthesis during the early action of thyroid hormones.
复制标题
甲状腺激素早期作用期间的核糖核酸合成。
作者：
J. Tata;C. Widnell
1.通过测定（a）离体细胞核中依赖于DNA的RNA聚合酶的活性，（B）体内细胞核和细胞质RNA的合成速率，（c）多聚核糖体沉降曲线，（d）微粒体和核糖核蛋白颗粒对多聚尿苷酸的反应，（e）离体细胞核中依赖于DNA的RNA聚合酶的活性，（f）离体细胞核中依赖于DNA的RNA聚合酶的活性，（g）离体细胞核中依赖于DNA的RNA（e）RNA和蛋白质合成抑制剂对激素生物活性的影响。2.甲状腺切除术可降低离体大鼠肝细胞核的DNA依赖性RNA聚合酶活性，并可通过给予三碘甲腺原氨酸或l-甲状腺素（2- 25 μ g/ml）刺激其活性。100克。体重）对正常和甲状腺切除的大鼠。在甲状腺切除的大鼠中，Mg（2+）激活的RNA聚合酶反应（其产物主要是核糖体类型的RNA）的活性在10- 12小时被刺激。单次注射三碘甲腺原氨酸后，在45小时达到峰值，刺激率为60-90%。激素治疗后。Mn（2+）/硫酸铵激活的RNA聚合酶反应（RNA产物更像DNA）在24小时内不受影响。但在45小时时刺激30-40%。两种RNA聚合酶反应在体内对激素的反应都与生理反应相同，但在体外将激素加入分离的细胞核中不会刺激酶。3. 3- 4小时内。甲状腺切除大鼠给予三碘甲腺原氨酸后，10分钟后，快速标记的核RNA的比活性。[6-（14）C]乳清酸脉冲的刺激值比对照值高30-40%，在11和16小时达到100%和200%。分别在激素给药后。长时间暴露于[6-（14）C]乳清酸和[（32）P]磷酸盐表明，该激素加速了线粒体、微粒体（或核糖体）和可溶性RNA的合成。标记的核RNA的大部分是核糖体类型。放射性前体掺入RNA中的放射性诱导的增加之前没有，但随后，通过增强前体的摄取。每克无变化。在35 - 45小时之间，核糖体RNA的含量增加了40-60%。在对甲状腺切除大鼠单次注射三碘甲状腺原氨酸后。4.与激素给药后核糖体RNA的增加相一致的是多聚核糖体的平均大小和数量的增加。激素处理后，新形成的核糖核蛋白颗粒或附着在其上的信使RNA或两者与微粒体膜结合得更牢固。5.与正常动物的制备物相比，多尿苷酸引起甲状腺切除大鼠的核糖核蛋白颗粒对[（14）C]苯丙氨酸掺入的更大刺激，但不引起微粒体的刺激。三碘甲状腺原氨酸治疗甲状腺切除大鼠后，核糖核蛋白颗粒对多聚尿苷酸的反应降低。6.放线菌素D、5-氟尿嘧啶、嘌呤霉素和放线菌酮对正常和甲状腺切除动物的基础代谢率和生长率的刺激作用均能抑制70-100%。放线菌素D的管理也取消了刺激RNA聚合酶的三碘甲腺原氨酸。7.它的结论是，调节核和核糖体RNA的合成是一个必不可少的步骤，导致甲状腺激素的生物作用，新的核糖体的形成是这些激素的细胞质蛋白质合成的控制的一个重要方面。
1. The effect on RNA synthesis in rat liver of thyroidectomy and the administration of thyroid hormone, especially during its physiological latent period, was studied by determining: (a) the activity of DNA-dependent RNA polymerase in isolated nuclei; (b) the rate of synthesis of nuclear and cytoplasmic RNA in vivo; (c) polyribosomal sedimentation profiles; (d) the response of microsomes and ribonucleoprotein particles to polyuridylic acid; (e) the effect of inhibitors of RNA and protein synthesis on the biological activity of hormones. 2. The DNA-dependent RNA-polymerase activity of isolated rat-liver nuclei was lowered by thyroidectomy and stimulated by the administration of tri-iodo-l-thyronine or l-thyroxine (2-25mug./100g. body wt.) to both normal and thyroidectomized rats. In thyroidectomized rats, the activity of the Mg(2+)-activated RNA-polymerase reaction (for which the product is mainly ribosomal type of RNA) was stimulated at 10-12hr. after a single injection of tri-iodothyronine, reaching a peak value of 60-90% stimulation at 45hr. after hormone administration. The Mn(2+)/ammonium sulphate-activated RNA-polymerase reaction (for which the RNA product is more DNA-like) was not affected for 24hr. after hormone administration but stimulated by 30-40% at 45hr. The response of both RNA-polymerase reactions to the hormone in vivo paralleled the physiological response but the enzyme was not stimulated by the addition in vitro of the hormone to isolated nuclei. 3. Within 3-4hr. after tri-iodothyronine administration to thyroidectomized rats, the specific activity of rapidly labelled nuclear RNA, after a 10min. pulse of [6-(14)C]orotic acid, was 30-40% greater than the control values, the stimulation reaching 100 and 200% at 11 and 16hr. respectively after hormone administration. Longer exposures to [6-(14)C]orotic acid and [(32)P]phosphate showed that the hormone accelerated the synthesis of mitochondrial, microsomal (or ribosomal) and soluble RNA. The greater part of the labelled nuclear RNA was of the ribosomal type. The hormone-induced increases in the incorporation of radioactive precursors into RNA were not preceded, but followed, by enhanced uptake of the precursor. There was no change, per g. of liver, of DNA, nuclear RNA or soluble RNA, but there was a 40-60% increase in the amount of ribosomal RNA between 35 and 45hr. after a single injection of tri-iodothyronine to thyroidectomized rats. 4. Coinciding with the increase in ribosomal RNA after hormone administration was an increase in the average size and amount of polyribosomes. The newly formed ribonucleoprotein particles, or messenger RNA attached to them, or both, were more firmly bound to microsomal membranes after hormone treatment. 5. Polyuridylic acid caused a bigger stimulation of incorporation of [(14)C]phenyl-alanine by ribonucleoprotein particles, but not by microsomes, from thyroidectomized rats as compared with preparations from normal animals. The response of ribonucleoprotein particles to polyuridylic acid was lowered after tri-iodothyronine treatment of thyroidectomized rats. 6. Actinomycin D, 5-fluorouracil, puromycin and cycloheximide caused a 70-100% inhibition of the stimulatory effect of l-thyroxine and tri-iodo-l-thyronine on basal metabolic rate and growth rate in both normal and thyroidectomized animals. Administration of actinomycin D also abolished the stimulation of RNA polymerase by tri-iodothyronine. 7. It is concluded that regulation of nuclear and ribosomal RNA synthesis is an essential step leading to the biological action of thyroid hormones and that the formation of new ribosomes is an important aspect of the control of cytoplasmic protein synthesis by these hormones.