Gubits R M, Lynch K R, Kulkarni A B, Dolan K P, Gresik E W, Hollander P, Feigelson P
J Biol Chem. 1984 Oct 25;259(20):12803-9.
The alpha 2u globulins, products of a highly homologous multigene family, are synthesized in the liver and submaxillary salivary glands of the rat. Although their precise function has not been ascertained, they are of interest because of the complex developmental and hormonal regulation of their tissue levels. We now report that alpha 2u globulin is synthesized in a third tissue of the rat, the extraorbital lachrymal gland. Immunocytochemical studies indicate that the distribution of alpha 2u globulin is more homogeneous in the lachrymal gland than in the liver or submaxillary gland. In situ hybridization to alpha 2u globulin RNA reveals specific signal only over the acinar cells of the lachrymal gland. Several different isoelectric forms of alpha 2u globulin are encoded by lachrymal gland mRNA. The major lachrymal and salivary gland isoforms are indistinguishable from one another, but more acidic than the hepatic isoforms. In addition, analysis of double-stranded cDNAs with a diagnostic restriction-enzyme pair detects no differences between the alpha 2u globulin mRNAs of lachrymal and salivary gland, but clearly distinguishes these from their hepatic counterparts. In spite of the similarity between the lachrymal and salivary gland alpha 2u globulin gene products, we find that the hormonal and developmental regulation of alpha 2u globulin expression differs markedly in these two tissues. In the liver, where a different subset of alpha 2u globulin genes is expressed, a third regulatory phenotype is observed.
α2u球蛋白是一个高度同源的多基因家族的产物，在大鼠的肝脏和颌下唾液腺中合成。尽管它们的确切功能尚未确定，但由于其组织水平受到复杂的发育和激素调节，因而备受关注。我们现在报告，α2u球蛋白在大鼠的第三个组织——眶外泪腺中合成。免疫细胞化学研究表明，α2u球蛋白在泪腺中的分布比在肝脏或颌下腺中更均匀。对α2u球蛋白RNA进行原位杂交仅在泪腺的腺泡细胞上显示出特异性信号。泪腺mRNA编码几种不同的α2u球蛋白等电形式。泪腺和唾液腺的主要同工型彼此无法区分，但比肝脏同工型更偏酸性。此外，用一对诊断性限制酶分析双链cDNA发现，泪腺和唾液腺的α2u球蛋白mRNA之间没有差异，但能将它们与肝脏中的α2u球蛋白mRNA清楚地区分开来。尽管泪腺和唾液腺的α2u球蛋白基因产物相似，但我们发现这两个组织中α2u球蛋白表达的激素调节和发育调节明显不同。在肝脏中，表达的是α2u球蛋白基因的不同亚组，观察到了第三种调节表型。
