Onoagbe I O
Department of Biochemistry, University of Maiduguri, Nigeria.
Arch Biochem Biophys. 1994 Feb 15;309(1):58-61. doi: 10.1006/abbi.1994.1084.
Hepatocytes were isolated from 17-day-old chick embryos. Steroid hormones or insulin, alone or when combined, did not alter tyrosine aminotransferase (TAT) activity in the isolated hepatocytes. However, TAT was stimulated by glucocorticoids in mixed hepatocyte and fibroblast cocultures; hormonal effects were not observed in pure hepatocyte cultures. Administration of hydrocortisone, dexamethasone, or triamcinolone (singly) to chick embryos in ovo resulted in an increase in hepatic TAT activity; insulin injection was without effect on the enzyme. The stimulation of TAT activity evoked by glucocorticosteroids in ovo was abolished by injection of cycloheximide or cordycepin. These observations contrast with reported glucocorticosteroid actions on TAT activity in fetal rat liver. It would appear that the differential regulatory effects on hepatic TAT by glucocorticosteroids are imposed by the distinct nutrient environments of chick embryos and fetal rats.
肝细胞从17日龄的鸡胚中分离出来。单独使用或联合使用类固醇激素或胰岛素，都不会改变分离出的肝细胞中酪氨酸转氨酶（TAT）的活性。然而，在肝细胞与成纤维细胞的混合共培养物中，糖皮质激素会刺激TAT；在纯肝细胞培养物中未观察到激素效应。对鸡胚进行卵内注射氢化可的松、地塞米松或曲安西龙（单独使用）会导致肝脏TAT活性增加；注射胰岛素对该酶没有影响。注射环己酰亚胺或虫草素可消除卵内糖皮质激素对TAT活性的刺激作用。这些观察结果与报道的糖皮质激素对胎鼠肝脏TAT活性的作用形成对比。看来，糖皮质激素对肝脏TAT的不同调节作用是由鸡胚和胎鼠不同的营养环境所施加的。
