Uterine peristalsis during the follicular phase of the menstrual cycle: effects of oestrogen, antioestrogen and oxytocin

Uterine peristalsis, directing sustained and rapid sperm transport from the external cervical os or the cervical crypts to the isthmic part of the tub e ipsilateral to the dominant follicle, changes in direction and frequency during the menstrual cycle, with lowest activity during menstruation and hi ghest activity at mid cycle. It was therefore suggested that uterine perist alsis is under the control of the dominant follicle with the additional inv olvement of oxytocin. To test this hypothesis? vaginal sonography of uterin e peristalsis was performed in the early, mid and late proliferative phases , respectively, of cycles of women treated with oestradiol valerate and wit h human menopausal gonadotrophin following pituitary downregulation, with c lomiphene citrate and with intravenous oxytocin, respectively. Administrati on of oestradiol valerate resulted in oestradiol serum concentrations compa rable with the normal cycle with a simulation of the normal frequency of pe ristaltic contractions. Elevated oestradiol concentrations and bolus inject ions of oxytocin resulted in a significant increase in the frequency of per istaltic contractions in the early and mid follicular phases, respectively. Chlomiphene tended, though insignificantly so, to suppress the frequency o f peristaltic waves in the presence of elevated oestradiol concentrations. In the late follicular phase of the cycle extremely elevated oestradiol con centrations as well as the injection of oxytocin resulted only in an insign ificant further increase of peristaltic frequency. In the normal cycles, as well as during extremely elevated oestradiol concentrations and following oxytocin administration, the peristaltic contractions were always confined to the subendometrial layer of the muscular wall. The results and the revie w of literature indicate that uterine peristalsis during the follicular pha se of the menstrual cycle is controlled by oestradiol released from the dom inant follicle with the probable involvement of oxytocin, which is presumab ly stimulated together with its receptor within the endometrial-subendometr ial unit and therefore acting in an autocrine/paracrine fashion. Since unph ysiological stimulation with oestradiol and oxytocin did not significantly increase the frequency of uterine peristalsis in the late follicular phase of the cycle it is assumed that normal preovulatory frequency of uterine pe ristalsis is at a level which cannot be significantly surpassed due to phen omena of refractoriness of the system.