EXPRESSION OF ENDOTHELIAL AND INDUCIBLE NITRIC-OXIDE SYNTHASE IN NONPREGNANT AND DECIDUALIZED HUMAN ENDOMETRIUM

Immunocytochemistry was used to localize endothelial (eNOS) and induci ble (iNOS) nitric oxide synthase in human uterine tissues collected at various stages of the menstrual cycle, after exposure to exogenous pr ogestagens, and in early pregnancy. Endothelial NOS-like immunoreactiv ity was detected in all specimens in endothelial cells lining blood ve ssels in the myometrium and endometrium, and in endometrial glandular epithelial cells. Inducible NOS-like immunoreactivity was also demonst rated in glandular epithelial cells. For both eNOS and iNOS there was considerable variation in the intensity of epithelial cell staining be tween samples, which was not related to the stage of the menstrual cyc le at which the tissue was collected. Messenger RNA for eNOS and iNOS was detected by reverse transcription-polymerase chain reaction (RT-PC R) using total RNA purified from isolated endometrial gland fragments. Immunoreactivity for eNOS and iNOS was not present in endometrial str oma throughout the menstrual cycle, but iNOS-like immuno-reactivity wa s seen in decidualized stromal cells both following treatment with exo genous progestagen (intrauterine L-norgestrel) and in tissues obtained in the first trimester of pregnancy. The detection of protein and mRN A for eNOS and iNOS in normal human endometrium suggests that NO may p lay a role in the local control of endometrial function.