Lee Nikki P Y, Cheng C Yan
Population Council, 1230 York Avenue, New York, New York 10021, USA.
Biol Reprod. 2004 Feb;70(2):267-76. doi: 10.1095/biolreprod.103.021329. Epub 2003 Oct 1.
During spermatogenesis, preleptotene and leptotene spermatocytes, residing in the basal compartment of the seminiferous epithelium, must traverse the blood-testis barrier (BTB) to gain entry to the adluminal compartment for further development at late stage VIII and early stage IX of the epithelial cycle. As such, the timely opening and closing of the BTB is crucial to spermatogenesis. A compromise in this process can lead to infertility. Moreover, the BTB is unique in its relative localization in the seminiferous epithelium compared to the tight junctions (TJs) found in other epithelia. Sertoli cell TJs are situated near the basal lamina in the testis, closest to the basement membrane (a modified form of extracellular matrix [ECM]), unlike TJs found in other epithelia, which are found nearest the apical portion of an epithelium, farthest away from ECM. Needless to say, BTB function in the testis is maintained by intricate regulatory mechanisms. In addition to hormones and cytokines, nitric oxide (NO) was recently shown to be a putative TJ regulator in the testis. Perhaps equally important, TJ dynamics in the testis were shown to be regulated, at least in part, by occludin, a TJ-integral membrane protein, via the NO/soluble guanylate cyclase/cGMP/protein kinase G signaling pathway. This minireview summarizes recent advances in the field regarding the role of NO in testicular function, with special emphasis regarding its role in TJ dynamics and the likely implications of these studies for male contraceptive development.
在精子发生过程中，位于生精上皮基底室的前细线期和细线期精母细胞必须穿过血睾屏障（BTB），以便在生精上皮周期的第八期晚期和第九期早期进入管腔室进行进一步发育。因此，BTB的适时开放和关闭对精子发生至关重要。这一过程中的任何妥协都可能导致不育。此外，与其他上皮组织中的紧密连接（TJ）相比，BTB在生精上皮中的相对定位是独特的。睾丸支持细胞的TJ位于睾丸的基膜附近，最靠近基底膜（细胞外基质[ECM]的一种修饰形式），这与其他上皮组织中的TJ不同，后者位于上皮的顶端部分附近，离ECM最远。不用说，睾丸中的BTB功能是由复杂的调节机制维持的。除了激素和细胞因子外，一氧化氮（NO）最近被证明是睾丸中一种假定的TJ调节因子。也许同样重要的是，睾丸中的TJ动态至少部分受闭合蛋白（一种TJ整合膜蛋白）通过NO/可溶性鸟苷酸环化酶/cGMP/蛋白激酶G信号通路的调节。这篇综述总结了该领域关于NO在睾丸功能中的作用的最新进展，特别强调了其在TJ动态中的作用以及这些研究对男性避孕发展的可能影响。
