School of Biology & Environmental Science, College of Life Sciences, University College Dublin, Belfield, Dublin, Ireland.
Br J Pharmacol. 2011 Dec;164(7):1780-92. doi: 10.1111/j.1476-5381.2011.01377.x.
In mammals, urea is the main nitrogenous breakdown product of protein catabolism and is produced in the liver. In certain tissues, the movement of urea across cell membranes is specifically mediated by a group of proteins known as the SLC14A family of facilitative urea transporters. These proteins are derived from two distinct genes, UT-A (SLC14A2) and UT-B (SLC14A1). Facilitative urea transporters play an important role in two major physiological processes - urinary concentration and urea nitrogen salvaging. Although UT-A and UT-B transporters both have a similar basic structure and mediate the transport of urea in a facilitative manner, there are a number of significant differences between them. UT-A transporters are mainly found in the kidney, are highly specific for urea, have relatively lower transport rates and are highly regulated at both gene expression and cellular localization levels. In contrast, UT-B transporters are more widespread in their tissue location, transport both urea and water, have a relatively high transport rate, are inhibited by mercurial compounds and currently appear to be less acutely regulated. This review details the fundamental research that has so far been performed to investigate the function and physiological significance of these two types of urea transporters.
在哺乳动物中，尿素是蛋白质分解代谢的主要含氮产物，由肝脏产生。在某些组织中，尿素穿过细胞膜的运动是由一组被称为 SLC14A 家族的易化尿素转运蛋白特异性介导的。这些蛋白来源于两个不同的基因，UT-A（SLC14A2）和 UT-B（SLC14A1）。易化尿素转运蛋白在两个主要的生理过程中发挥重要作用——尿液浓缩和尿素氮回收。虽然 UT-A 和 UT-B 转运蛋白具有相似的基本结构，并且以易化的方式介导尿素的转运，但它们之间存在许多显著的差异。UT-A 转运蛋白主要存在于肾脏中，对尿素具有高度特异性，转运速率相对较低，并且在基因表达和细胞定位水平都受到高度调节。相比之下，UT-B 转运蛋白在组织中的分布更为广泛，既能转运尿素又能转运水，转运速率相对较高，受汞化合物抑制，目前似乎受到的调节不太敏感。本综述详细介绍了迄今为止为研究这两种类型的尿素转运蛋白的功能和生理意义而进行的基础研究。
