NITRIC OXIDE CGMP PATHWAY COMPONENTS IN THE LEYDIG-CELLS OF THE HUMANTESTIS/

In this study we sought to determine whether the main components of th e nitric oxide (NO) pathway are localized within the Leydig cells of t he human testis and whether the soluble guanylyl cyclase (sGC), the en zyme that accounts for NO effects, is functionally active in these cel ls. Using an amplified immunocytochemical technique, immunoreactivity for nitric oxide synthase (NOS-I), sGC and cyclic guanosine monophosph ate (cGMP) was detected within the cytoplasm of human Leydig cells. Di stinct differences in staining intensity were found between individual Leydig cells, between cell groups and between Leydig cells of differe nt patients. By means of a specific cGMP-RIA, a concentration-dependen t increase in the quantity of cGMP was measured in primary cultures of human Leydig cells following exposure to the NO donor sodium nitropru sside. In addition, NOS-I immunoreactivity was seen in Sertoli cells, whereas cGMP and sGC immunoreactivity was found in Sertoli cells, some apically situated spermatids and residual bodies of seminiferous tubu les. Dual-labelling studies and the staining of consecutive sections s howed that there are several populations of Leydig cells in the human testis. Most cells were immunoreactive for NOS-I, sGC and cGMP, but sm aller numbers of cells were unlabelled by any of the antibodies used, or labelled for NOS-I or cGMP alone, for sGC and cGMP, or for NOS-I an d sGC. These results show that the Leydig cells possess both the enzym e by which NO is produced and the active enzyme which mediates the NO effects. There are different Leydig cell populations that probably ref lect variations in their functional (steroidogenic) activity.