Haefliger J A, Demotz S, Braissant O, Suter E, Waeber B, Nicod P, Meda P
Department of Internal Medicine, Laboratory of Clinical Chemistry, Division of Physiopathology, University Hospital, Lausanne, Switzerland.
Kidney Int. 2001 Jul;60(1):190-201. doi: 10.1046/j.1523-1755.2001.00786.x.
Connexin 40 (Cx40) is a gap junction protein expressed in endothelial cells of vessels, endocardium, and conducting cells of the His-Purkinje system of heart. Its distribution in the kidney remains to be fully investigated.
To address this distribution, we generated rabbit antibodies directed to a polypeptide comprising amino acids 231 to 330 of the carboxy-terminal domain of rodent Cx40, which specifically recognizes this protein at gap junctions.
Immunolabeling and in situ hybridization of kidney sections showed that Cx40 and its transcript were coexpressed by most endothelial cells of vessels and glomeruli, as well as by renin-secreting cells. This distribution contrasted with that of Cx43, which was expressed in some tubules of medulla and sparse endothelial cells. Cx40 and Cx43 expression were investigated further in a renin-dependent model of hypertension, in which rats showed an increase in arterial mean blood pressure four weeks after clipping one renal artery [two kidney, one-clip (2K1C) model]. Northern blot analysis of polyA+ RNA demonstrated that, compared with sham-operated animals, the hypertensive 2K1C animals featured an increase in Cx40 mRNA expression in both left (clipped) and right (unclipped) kidneys. In contrast, Cx43 mRNA expression was only increased in the latter organ. Antibodies confirmed that the levels of Cx40 were actually increased in the kidneys of hypertensive animals (Western blots) and this was caused, at least in part, by enhanced expression of this protein in the renin-secreting cells of the afferent arteriole (immunofluorescence).
Cell-to-cell communication mediated by Cx40 may be implicated in the function of renin-secreting cells, hence participating in the control of blood pressure.
连接蛋白40（Cx40）是一种在血管内皮细胞、心内膜以及心脏希氏-浦肯野系统的传导细胞中表达的间隙连接蛋白。其在肾脏中的分布仍有待充分研究。
为了研究这种分布情况，我们制备了针对包含啮齿动物Cx40羧基末端结构域第231至330位氨基酸的多肽的兔抗体，该抗体可在间隙连接处特异性识别此蛋白。
肾脏切片的免疫标记和原位杂交显示，Cx40及其转录本在血管和肾小球的大多数内皮细胞以及肾素分泌细胞中共同表达。这种分布与Cx43不同，Cx43在髓质的一些肾小管和稀疏的内皮细胞中表达。在肾素依赖性高血压模型中对Cx40和Cx43的表达进行了进一步研究，在该模型中，大鼠在夹闭一侧肾动脉四周后动脉平均血压升高（两肾一夹（2K1C）模型）。对多聚腺苷酸加尾RNA的Northern印迹分析表明，与假手术动物相比，高血压2K1C动物的左（夹闭）右（未夹闭）肾中Cx40 mRNA表达均增加。相比之下，Cx43 mRNA表达仅在后者器官中增加。抗体证实高血压动物肾脏中Cx40的水平实际上升高了（蛋白质免疫印迹法），并且这至少部分是由于该蛋白在入球小动脉肾素分泌细胞中的表达增强所致（免疫荧光法）。
由Cx40介导的细胞间通讯可能与肾素分泌细胞的功能有关，从而参与血压的调控。
