Nitric Oxide Synthase(NOS-I) in Leydig Cells of the Human Testis.

Abstract

By means of immunocytochemical methods, immunoreactivity for the brain isoform of nitric oxide synthase (NOS-I) was recognized in numerous Leydig cells of the human testis as well as in MA-10 tumor and TM3 non-tumor mouse Leydig cell lines. Within the Leydig cell cytoplasm, immunocytochemical results suggested the occurrence of factors known to activate NOS-I such as glutamate and aspartate, as well as molecules involved in the regulation of the NOS-I activity such as calmodulin and Ca2+/calmodulin-dependent protein kinase II. Leydig cells, Sertoli cells, some endothelial cells of the testis, MA-10- and TM3 mouse Leydig cell lines exhibited a relatively strong NADPH-diaphorase enzyme activity as well. Double sequential immunostainings provided evidence that NOS-like immunoreactivity of the testicular Leydig cells is colocalized with testosterone, calmodulin, aspartate, glutamate, and Ca2+/calmodulin-dependent protein kinase II. Sodium nitro-prusside treatment did not result in increased cGMP formation by MA-10- or TM3 mouse Leydig cells, suggesting that NO produced by these cells acts primarily in a paracrine fashion. The NO produced by NOS-I immunoreactive Leydig cells may act as a messenger: 1) between neighbouring NOS-I positive and/or negative Leydig cells as well as to mediate the action of numerous intracellular and extracellular neuroactive substances and growth factors; 2) between Leydig cells and the muscle cells or pericytes of blood vessels to regulate local blood flow and permeability; and 3) between Leydig cells and pertibular myofibroblasts to influence their contraction and the permeability of the lamina propria.

An Alternative Promoter of the Human Neuronal Nitric Oxide Synthase Gene Is Expressed Specifically in Leydig Cells

“…Similar to that of the Ϫ6500/ϩ81 TnNOS/lacC/␣ 1 G transgene, expression of native nNOS varied among individual Leydig cells and Leydig cell groups. This phenomenon has been observed in human testis where subpopulations of Leydig cells have also been defined, 5 as in the murine setting. In addition to the Leydig cells, weaker nNOS-like immunoreactivity was also detected in spermatogonia, spermatocytes, and spermatids, as well as Sertoli cells of the seminiferous tubules ( Figure 5B).…”

“…[53][54][55][56][57] NO, produced in Leydig cells, plays multiple roles in testicular biology. 5,25,58 Leydig cells, located in the interstitium of the testis, function as the primary site for the synthesis of testosterone. Exogenous NO is a dual modulator of testosterone synthesis and release, being stimulatory at low and inhibitory at high concentrations.…”

“…Specifically, NO produced from Tn-NOS-positive Leydig cells may act on these same cells as an intercellular and intracellular signaling molecule. 5 The gene encoding nNOS was disrupted via targeted replacement of exon 2 obviating synthesis of full-length transcripts. Given the importance of NO in penile erectile function, 5,59,60 it could be argued that the ability of the nNOS(Ϫ/Ϫ) mice to reproduce was somewhat surprising.…”

“…However, not every Leydig cell showed positive staining and signal intensity varied among those stained positive, consistent with the reported existence of subpopulations within this cell type. 5 Vascular cells within the interstitial area stained negative for ␤-galactosidase (Figure 3B). There was no background ␤-galactosidase staining in transgene-negative testis ( Figure 3C).…”

“…3 For instance, nNOS plays a fundamental role in the regulation of male sexual function. Lines of evidence have indicated the involvement of nNOS in penile erection, 4 in testosterone synthesis in the Leydig cells of the testis, 5,6 in sexual behavior, [7][8][9] and in egg activation at fertilization, 10 among others. Understanding the molecular regulation of nNOS in male sexual organs may be relevant to potential therapeutic measures in male sexual dysfunction.…”