Banjo A O, Nemeth A M
J Cell Biol. 1976 Aug;70(2 pt 1):319-25. doi: 10.1083/jcb.70.2.319.
UDP-Glucuronyltransferase (GT) activity increases in chick embryo liver during culture from zero to a steady-state level at or above adult values. The GT activity (o-aminophenol as acceptor) is located entirely in the membranes of the endoplasmic reticulum (ER) and the question arises whether ER increases along with GT. Earlier work showed that the synthesis and degradation rates of GT can be varied in culture over wide ranges by choosing embryo livers of different ages and both phenobarbital. In the present study we measured the GT activities and the concentrations of ER (using stereologic methods) in 5- and 11-day embryo liver during culture with and without phenobarbital. We found that GT and ER always increased in a constant ratio of 2.2 X 10(-9) U of GR activity per square micrometer of membrane, suggesting that the synthesis and degradation of GT are coupled to the synthesis and degradation of ER. A general structure for ER is proposed to explain this finding.
在培养过程中，鸡胚肝脏中的尿苷二磷酸葡萄糖醛酸基转移酶（GT）活性从零增加到稳定状态水平，达到或超过成年鸡的水平。GT活性（以邻氨基酚为受体）完全位于内质网（ER）膜中，因此出现了内质网是否随GT一起增加的问题。早期的研究表明，通过选择不同年龄的胚胎肝脏以及苯巴比妥，在培养过程中GT的合成和降解速率可以在很宽的范围内变化。在本研究中，我们测量了在添加和不添加苯巴比妥的培养过程中，5日龄和11日龄胚胎肝脏中的GT活性以及内质网的浓度（使用体视学方法）。我们发现，GT和内质网总是以每平方微米膜2.2×10⁻⁹U的GT活性的恒定比例增加，这表明GT的合成和降解与内质网的合成和降解相关联。提出了内质网的一般结构来解释这一发现。
