Cake M H, Ho K K, Shelly L, Milward E, Yeoh G C
School of Biological and Environmental Sciences, Murdoch University, Western Australia.
Eur J Biochem. 1989 Jun 15;182(2):429-35. doi: 10.1111/j.1432-1033.1989.tb14849.x.
Previous studies have shown that insulin depresses the induction of tyrosine aminotransferase by glucocorticoids in cultured fetal rat hepatocytes. However, the site at which this inhibitory effect is exerted was not elucidated, since only enzyme activity was determined in such studies. Therefore, the effect of insulin on tyrosine aminotransferase synthesis, the level of its mRNA as well as the rate of transcription of the gene in isolated nuclei have been determined. The results obtained indicate that in cultures exposed to dexamethasone, Bt2cAMP, insulin and combinations of these additives, there is an excellent correlation between the enzyme activity, enzyme synthesis and the level of mRNA. Run-on transcription experiments indicate that the reduction in the level of mRNA by insulin in dexamethasone-supplemented cultures is the result of a diminished rate of gene transcription.
以往的研究表明，胰岛素可抑制糖皮质激素对培养的胎鼠肝细胞中酪氨酸转氨酶的诱导作用。然而，由于此类研究仅测定了酶活性，所以并未阐明这种抑制作用的发挥位点。因此，已测定了胰岛素对酪氨酸转氨酶合成、其mRNA水平以及分离细胞核中该基因转录速率的影响。所得结果表明，在暴露于地塞米松、Bt2cAMP、胰岛素以及这些添加剂组合的培养物中，酶活性、酶合成与mRNA水平之间存在良好的相关性。连续转录实验表明，在补充了地塞米松的培养物中，胰岛素导致的mRNA水平降低是基因转录速率下降的结果。
