Abstract
In monocytes at the secretory (oestrogen-progesterone dominant) phase of the menstrual cycle, expression of c-fms and macrophage colony-stimulating factor (M-CSF) receptor and activity of tyrosine kinase (TK) were increased by oestradiol with or without progesterone. In vivo, oestrogen may induce expression of c-fms and M-CSF receptor as well as the activation of TK in monocytes under the milieu of the secretory phase. Alternatively, cells of monocyte lineage during the secretory phase might, via various factors, obtain the potency to induce the expression and the function of M-CSF receptors, this potency being effected by oestrogen. Macrophages in peritoneal fluid in pelvic endometriosis (oestrogen predominant) might be activated during the secretory phase of the menstrual cycle, causing infertility.