Preferential vascular-based transfer from vagina to the corpus but not to the tubal part of the uterus in postmenopausal women.

BACKGROUND: Vaginal administration of progesterone during infertility treatment has therapeutic advantages over oral administration. However, the reasons for this are poorly defined. To demonstrate a preferential vagina-to-uterus distribution of substances, we investigated cold distribution from vagina to the uterus and rectum. METHOD: In 10 postmenopausal women, thermoprobes were inserted into the uterine cavity and in the rectum at <9 cm or at >9 cm from the anus; temperatures were subsequently measured during 10 min flushing of vagina with cold saline. RESULTS: After 10 min, temperature decreased as follows: uterus, tubal angle: -0.22 +/- 0.07 degrees C, 10 (mean +/- SEM, n); uterus, middle cavity: -1.26 +/- 0.34 degrees C, 9; rectum, <9 cm insertion: -3.69 +/- 0.68 degrees C, 3; rectum, >9 cm insertion: -0.51 +/- 0.19 degrees C, 6. CONCLUSIONS: Despite obviously different distances to the vagina of the uterine and the low rectal probes (<9 cm) the temperature decrease occurred at the same time. Cold transfer from vagina to the uterus and rectum is probably not the result of simple diffusion but of a vascular counter-current transfer. Differential cooling of corpus and tubal angles suggests a different arterial supply; while uterine corpus is supplied from the uterine artery, the tubal angles seem to be mainly supplied from the ovarian artery via the tubal arcade.