NOS3 and Infertility: In summary, although there are inconsiderable differences in expression of endothelial nitric oxide synthase in stroma, glandular epithelium and vascular endothelium of endometrial tissues of women with unexplained infertility, but changes in expression of enzyme in luminal epithelium suggests that eNOS may be involved in infertility phenomenon of these patients at the stage of implantation, results at least in changes in endometrial receptivity.