Sonographic evidence for the involvement of the utero-ovarian counter-current system in the ovarian control of directed uterine sperm transport.

Sperm transport from the cervix into the tube is an important uterine function within the process of reproduction. This function is exerted by uterine peristalsis and is controlled by the dominant ovarian structure via a cascade of endocrine events. The uterine peristaltic activity involves only the stratum subvasculare of the myometrium, which exhibits a predominantly circular arrangement of muscular fibres that separate at the fundal level into the fibres of the cornua and continue into the circular muscles of the respective tubes. Since spermatozoa are transported preferentially into the tube ipsilateral to the dominant follicle, this asymmetric uterine function may be controlled by the ovary via direct effects utilizing the utero-ovarian counter-current system, in addition to the systemic circulation. To test this possibility the sonographic characteristics of the uterine vascular bed were studied during different phases of the menstrual cycle. Vaginal sonography with the measurement of Doppler flow characteristics of both uterine arteries and of the arterial anastomoses of the uterine and ovarian arteries (junctional vessels) in the cornual region of both sides of the uterus during the menstrual phase of regular-cycling women demonstrated significant lower resistance indices of the junctional vessels ipsilateral to the side of the dominant ovarian structure as compared with the corresponding arteries contralaterally. By the use of the perfusion mode technique, it could be observed that vascular perfusion of the fundal myometrium was significantly increased ipsilateral to the dominant follicle during the late follicular phase of the cycle. These results show that the endocrine control of the dominant ovarian structure over uterine function is not only exerted via the systemic circulation but also directly, most probably utilizing the utero-ovarian counter-current system.