过多的尿素对心脏有损害作用。心脏尿素增多常见于心肌代谢增强(如心肌肥大)及肾功能损害导致的尿毒症。尿素通过细胞膜由尿素通道转运蛋白（UT）介导。心脏表达UT-A尿素转运蛋白, 但其基因一直未能克隆出来，严重制约了心脏尿素及尿素转运蛋白的研究。近期我们从大鼠心脏cDNA基因文库中成功克隆出UT-A基因，新命名为UT-A7。我们推测UT-A7在心脏转运尿素及防止过多尿素对心脏损害方面起着重要的作用。本研究内容：(1) 体外以培养的心肌细胞及稳转UT-A7 MDCK细胞；(2)体内实验以大鼠5/6肾切除尿毒症动物模型为研究对象, 通过基因转染过表达, RNA干扰等一系列技术研究UT-A7对心肌细胞的保护作用以及UT-A7调控机制及信号转导通路。本研究旨在探明尿素转运蛋白UT-A7在生理及病理情况下对心脏的调节作用，为将来可能通过干预尿素转运蛋白以达到改善心肌功能，延缓心脏损害提供理论依据。

Excess urea impairs heart function. Increased heart urea occurs either from enhanced protein metabolism (heart hypertrophy) or increased serum urea (uremic caused by end-stage renal disease). Urea across cell membrane is mediated by facilitated transport membrane proteins. Although that the heart expresses urea transport UT-A proteins has been recognized for many years, the gene has not yet been successfully cloned, which significantly impedes urea and urea transporter study in heart. By using a multiple PCR technology, we recently cloned UT-A gene from rat heart cDNA library. Interestingly, the heart UT-A gene is unique and structurally different from any member of the reported UT-A family gene. We name it as UT-A7. Here, we propose that UT-A7 may play an important role in mediating urea exit from cardiac myocyte under physiological conditions and protecting cardiac myocyte from urea toxicity in disease conditions. In this project, we will determine whether UT-A7 could protect cardiac myocytes caused by increased urea as well as the regulatory mechanism of signaling pathways. To fulfill our goal, both in vitro study (primary cultured cardiac myocytes, MDCK cells stably expressing UT-A7) and in vivo study (5/6 nephrectomized uremic rat animal model) will be used. A series of approaches including gene transfection, siRNA, etc will be employed. We hope that our study will provide the rationale for the potential therapeutic intervention of cardiac damage caused by urea overloading disease such as heart hypertrophy and uremic cardiomyopathy.