Endothelin-1 and big endothelin-1 increase in human endometrium during menstruation

OBJECTIVES: Although the physiologic and pathologic roles of endothelin-1 in reproduction have been investigated, little is known about human uterine tissue levels. We studied the levels of immunoreactive endothelin-1 and immunoreactive big endothelin-1 in human endometrium and myometrium during each menstrual phase. STUDY DESIGN: Materials were obtained at hysterectomy (endometrium, n = 33; myometrium, n = 27). We measured immunoreactive endothelin-1 and immunoreactive big endothelin-1 by radioimmunoassay and performed an immunohistochemical study of the tissue. Data were analyzed by the Mann-Whitney U test. RESULTS: We detected larger amounts of immunoreactive endothelin-1 and immunoreactive big endothelin-1 in the endometrium than in the myometrium throughout the menstrual, proliferative, and secretory phases. Endometrial immunoreactive endothelin-1 and immunoreactive endothelin-1 were significantly increased in the menstrual phase (endothelin-1 68.8 ± 23.3 pg/mg protein, n = 5, p< 0.005; big endothelin-1 45.2 ± 5.7 pg/mg protein, n = 5, p< 0.003) compared with the other phases (endothelin-1 30.7 ± 9.5 and 30.5 ± 14.0 pg/mg protein; big endothelin-1 19.9 ± 6.7 and 24.1 ± 7.4 pg/mg protein). Immunohistochemistry demonstrated that the endometrial stromal cells were positive for antiendothelin monoclonal antibody only in the premenstrual and menstrual phases. CONCLUSION: Levels of immunoreactive endothelin-1 and immunoreactive big endothelin-1 are different in each type of uterine tissue and in each phase of the menstrual cycle. These changes may indicate some role of endothelin-1 in menstruation.