Segmental Expression of the Bradykinin Type 2 Receptor in Rat Efferent Ducts and Epididymis and Its Role in the Regulation of Aquaporin 9
Segmental Expression of the Bradykinin Type 2 Receptor in Rat Efferent Ducts and Epididymis and Its Role in the Regulation of Aquaporin 9
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DOI：
10.1095/biolreprod.108.070797
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发表时间：
2009-01-01
影响因子：
3.6
通讯作者：
Breton, S.
中科院分区：
文献类型：
--
作者：
Belleannee, C.;Da Silva, N.;Breton, S.
水和溶质在输出管和附睾中的运输对于建立精子成熟和储存的适当管腔环境是重要的。水通道蛋白9（AQP 9）是附睾中的主要水通道，但其调控机制仍知之甚少。激肽-激肽释放酶系统（KKS）的组分，导致缓激肽（BK）的产生，在男性生殖道的管腔中高度表达。我们在这里报告，附睾腔液含有大量的BK（2 nM）。激光捕获显微切割（LCM）分离的附睾上皮细胞进行RT-PCR显示丰富的BK 2型受体（Bdkrb 2）mRNA表达，但没有1型受体（Bdkrb 1）。BDKRB 2和阴离子交换剂AE 2（输出管纤毛细胞的标志物）或V-ATP酶E亚基（官方符号ATP 6V 1 E1（附睾透明细胞的标志物））的双重免疫荧光染色显示，BDKRB 2在无纤毛细胞（输出管）和主细胞（附睾）的顶端表达。BDKRB 2、AQP 9和ATP 6V 1 E1的三重标记显示BDKRB 2和AQP 9共定位于附睾尾主细胞的顶端静纤毛中。虽然在传出管和沿着附睾小管中检测到均匀的Bdkrb 2 mRNA表达，但在蛋白水平上检测到显著的变化。BDKRB 2在输出管和附睾尾中最高，在远端起始段中居中，在体部中中等，在近端起始段和头中检测不到。对从远端初始段分离的小管的功能测定表明，BK显着增加AQP 9依赖性甘油顶端膜的通透性。这种作用被BAPTA-AM抑制，表明钙参与了这一过程。因此，这项研究确定BK是AQP 9的重要调节因子。
Water and solute transport in the efferent ducts and epididymis are important for the establishment of the appropriate luminal environment for sperm maturation and storage. Aquaporin 9 (AQP9) is the main water channel in the epididymis, but its regulation is still poorly understood. Components of the kinin-kallikrein system (KKS), leading to the production of bradykinin (BK), are highly expressed in the lumen of the male reproductive tract. We report here that the epididymal luminal fluid contains a significant amount of BK (2 nM). RT-PCR performed on epididymal epithelial cells isolated by laser capture microdissection (LCM) showed abundant BK type 2 receptor (Bdkrb2) mRNA expression but no type 1 receptor (Bdkrb1). Double-immunofluorescence staining for BDKRB2 and the anion exchanger AE2 (a marker of efferent duct ciliated cells) or the V-ATPase E subunit, official symbol ATP6V1E1 (a marker of epididymal clear cells), showed that BDKRB2 is expressed in the apical pole of nonciliated cells (efferent ducts) and principal cells (epididymis). Triple labeling for BDKRB2, AQP9, and ATP6V1E1 showed that BDKRB2 and AQP9 colocalize in the apical stereocilia of principal cells in the cauda epididymidis. While uniform Bdkrb2 mRNA expression was detected in the efferent ducts and along the epididymal tubule, marked variations were detected at the protein level. BDKRB2 was highest in the efferent ducts and cauda epididymidis, intermediate in the distal initial segment, moderate in the corpus, and undetectable in the proximal initial segment and the caput. Functional assays on tubules isolated from the distal initial segments showed that BK significantly increased AQP9-dependent glycerol apical membrane permeability. This effect was inhibited by BAPTA-AM, demonstrating the participation of calcium in this process. This study, therefore, identifies BK as an important regulator of AQP9.