ENDOTHELIN AND MENSTRUATION

Endothelin (ET) and its mRNA are present in human endometrium, Its exp ression varies across the menstrual cycle, reaching maximal levels in the pre-menstrual phase, Human endometrial epithelial cells are the ma jor in-vitro source of ET, and its release is affected by the stage of the menstrual cycle from which the endometrium is taken and by the cy tokines transforming growth factor-beta(1) and interleukin-1 alpha. Th e cyclical variation in both ET mRNA and protein expression across the normal menstrual cycle, and the differences observed in abnormal uter ine bleeding (specifically reduced immunoreactivity in luminal and gla ndular epithelium in the endometrium of Norplant(R) users), are consis tent with a;role for ET in the control of menstrual bleeding, The role of epithelial cell ET is not yet understood, Whether this source of E T is important in endometrial regeneration and repair following menstr uation or in vasoconstriction to cease menstrual bleeding remains to b e determined.