Intra-ovarian dynamic blood flow in pseudopregnant rabbits during prostaglandin F2α-induced luteolysis.

In the present study, we evaluated the dynamic changes of intra-ovarian blood flow, by real time color-coded and pulsed Doppler ultrasonography, as well as the immunopresence of prostaglandin F2α (PGF2α) receptor (FP) and peripheral plasma progesterone concentrations in pseudopregnant rabbit after PGF2α treatments at either early- (4 days) and mid-luteal (9 days) stages. During the pre-treatment observation interval of one hour, the ovarian blood flows showed a fluctuating pattern. Independently of luteal stage, PGF2α administration caused a four-fold decline in the blood flow within 40 min that was, followed 50 min later by a reactive hyperemia that lasted several hours, while the resistive index showed an opposite trend. Twenty-four hr later the blood flow was one half that measured before PGF2α injection. At day 4 of pseudopregnancy PGF2α did not affect peripheral plasma progesterone concentrations, but at day 9 it caused functional luteolysis as progesterone levels declined 6 h later to reach basal values after 24 hr. The changes in the ovarian blood flows of pseudopregnant rabbits receiving PGF2α were accompanied by simultaneous changes in the resistance index. This biphasic response in the blood flow and vascular resistances likely reflects reactive hyperemia following vasoconstriction. By immunohistochemistry, strong positive immune reaction for FP was detected in the cytoplasm of endothelial cells of ovarian arteries, veins, and capillaries. In conclusion these results suggest that PGF2α could acutely regulates the ovarian blood flow of pseudopregnant rabbits, even if there is no evidence of a blood flow reduction anticipating luteolysis. This article is protected by copyright. All rights reserved.