Minireview

Nitric Oxide/Nitric Oxide Synthase, Spermatogenesis, and Tight Junction Dynamics

Abstract
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 when compared to tight junctions (TJs) found in other epithelia. It is noted that 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 present 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, 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/sGC/cGMP/PKG signaling pathway. This mini-review summarizes recent advances in the field regarding the role of NO in testicular function with special emphasis on its role in TJ dynamics and the likely implication of these studies in male contraceptive development.

Key words: Cyclic adenosine monophosphate • Cyclic guanosine monophosphate • Nitric oxide • Signal transduction • Spermatogenesis

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