Ovarian real-time blood flow changes in rabbits during PGF2a-induced luteolysis

The dynamic change of ovarian blood flow was monitored bypower Doppler ultrasonography in both oestrous and pseu-dopregnant rabbits before and after treatments with a luteo-lytic dose of PGF2a. Pseudopregnancy was induced by 20 IUeCG followed 2 days later by 0.8lg GnRH (day 0). Inoestrous rabbits, PGF2achallenge caused a transitory reduc-tion (p < 0.05) of ovarian blood flow, evaluated with thenumber of pixel recorded, within 20 min. By 50 min afterPGF2a, the blood flow returned to basal values, but thereafterit gradually increased to almost two-fold (p < 0.01) 90 min later. At either days 4 or 9 of pseudopregnancy, the ovarianblood flow was two- to three-fold (p < 0.01) greater than thatfound in oestrous does. After PGF2aadministration, thehaemodynamic changes in blood flow were similar to thoseobserved in oestrous rabbits, but more relevant, being char-acterized by a transitory, four-fold decrease (p < 0.01) at40 min followed by a rebound peak 90 min later and then by agradual decrease to approximately 50% of the basal values 12and 24 h later. Plasma progesterone concentrations declined(p < 0.01) within 6 h after PGF2a, only in day 9 pseudo-pregnant rabbits. These results confirm that the local vascularmechanisms controlling ovarian blood flow are not acutelyresponsible of the luteolytic effects of PGF2acausing proges-terone decline.