Identification of nitric oxide synthase in human uterus.

The aim of this study was to investigate the presence of nitric oxide synthase (NOS) in human uterus. Tissues were obtained at operation from 10 women undergoing hysterectomy for benign disease. In-situ hybridization was used to determine the distribution of mRNA for NOS with a 483 bp digoxigenin-labelled antisense riboprobe. Localization of NOS was detected by (i) immunocytochemistry using a monoclonal antibody raised against bovine constitutive endothelial NOS, and (ii) NADPH diaphorase, which has been suggested to co-localize with brain NOS. Messenger RNA for NOS was detected in endometrium and myometrium from nine of 10 women, predominantly in endometrial glandular epithelium and stroma and myometrial blood vessels. NOS-like immunoreactivity was seen in endometrial stroma and myometrial blood vessels, whereas NADPH diaphorase activity was localized mainly to endometrial glandular epithelium and myometrial blood vessels. These studies suggest that different forms of constitutive NOS are present in human endometrium and myometrium, and that nitric oxide may play a role in the paracrine control of the uterine vascular bed.