Borthwick E B, Coughtrie M W, Burchell A
Department of Biochemical Medicine, University of Dundee, Ninewells Hospital and Medical School, Scotland, U.K.
J Steroid Biochem Mol Biol. 1995 Nov;55(2):255-9. doi: 10.1016/0960-0760(95)00173-w.
We have examined the effects of hypophysectomy and treatment with thyroxine (T4) on enzyme activity and expression (as determined by immunoblot analysis) of members of the three principal sulfotransferase (ST) sub-families (phenol STs, PST; estrogen STs, EST; hydroxysteroid STs, HST) in cytosols prepared from female Wistar rat livers. The results demonstrate that in female rat liver cytosol, EST activity was decreased by treatment with T4, increased following hypophysectomy and that treatment of hypophysectomized animals with T4 also greatly reduced EST activity. T4 had no significant effect on PST or HST activity in normal animals, but it decreased HST activity in hypophysectomized rat liver cytosol. Immunoblot analysis of these cytosols with antibodies recognising HST and PST indicated that where changes in enzyme activity occurred they mirrored changes in enzyme protein expression. In normal adult female rat livers, EST protein is not expressed, and the small residual activity results predominantly from the action of HST. Hypophysectomy induced EST activity and the expression of EST enzyme protein in female rat liver cytosol, and T4 treatment of hypophysectomized animals reduced the activity to below normal levels without reducing the corresponding enzyme protein levels, indicating that T4 regulation of EST in females is via a post-translational mechanism.
我们研究了垂体切除及甲状腺素（T4）处理对从雌性Wistar大鼠肝脏制备的胞质溶胶中三种主要磺基转移酶（ST）亚家族（酚类STs，PST；雌激素STs，EST；羟类固醇STs，HST）成员的酶活性及表达（通过免疫印迹分析测定）的影响。结果表明，在雌性大鼠肝脏胞质溶胶中，EST活性经T4处理后降低，垂体切除后升高，且用T4处理垂体切除的动物也会大幅降低EST活性。T4对正常动物的PST或HST活性无显著影响，但会降低垂体切除大鼠肝脏胞质溶胶中的HST活性。用识别HST和PST的抗体对这些胞质溶胶进行免疫印迹分析表明，酶活性发生变化的地方反映了酶蛋白表达的变化。在正常成年雌性大鼠肝脏中，EST蛋白不表达，少量残留活性主要源于HST的作用。垂体切除诱导了雌性大鼠肝脏胞质溶胶中EST活性及EST酶蛋白的表达，用T4处理垂体切除的动物会使活性降至正常水平以下，而不会降低相应的酶蛋白水平，这表明T4对雌性EST的调节是通过翻译后机制实现的。
