ENDOTHELIN SYNTHESIS AND RECEPTORS IN HUMAN ENDOMETRIUM THROUGHOUT THE NORMAL MENSTRUAL-CYCLE

This study was undertaken to investigate the presence of messenger RNA (mRNA) for prepro-endothelin-I (ET-1) and the known receptor subtypes (ET(A) and ET(B)) in human endometrium at different stages of the menstrual cycle obtained at hysterectomy. Northern blot analysis revealed expression of ET-1 mRNA in human endometrium during the normal menstrual cycle, The concentration of ET-1 mRNA in endometrial tissue was greater during the menstrual and proliferative phases than during the ovulatory and secretory phases. Immunoreactive ET-1 was secreted into the medium of isolated endometrial stromal cells. Oestradiol and progesterone significantly attenuated ET-1 release in endometrial stromal cells cultured for 6 days. ET(A) and ET(B) mRNA were also present in endometrial tissue of the normal cycle. The concentration of ET(A) receptor mRNA was greater in the proliferative phase than in the secretory phase, whereas expression of ET(B) mRNA increased in menstrual phase. ET-1 significantly increased extracellular accumulation of cyclic AMP (cAMP), intracellular generation of inositol phosphates and significantly enhanced DNA synthesis in cultured endometrial stromal cells from the proliferative phase, Our results showed that human endometrial cells synthesized and released ET-1, and contained ET(A) and ET(B) receptors which were functionally coupled to phosphoinositide breakdown and to adenylate cyclase with the increase of cAMP by ET-1 stimulation. Our findings suggest that ET-1 may have a potential autocrine and/or paracrine function in human endometrial stromal cells.