Submission Number: LAU-4-99-126
Abstract Number: 386
ROLE OF ESTROGEN AND PROGESTERONE IN THE CONTROL OF UTERINE EDEMA IN PONY MARES.
LM Pelehach 1, DC Sharp 1, MB Porter 1, LN Dixon 1 and Karen J McDowell 2
Dept of Animal Science, Univ of Florida, Gainesville, Florida 1
Dept of Veterinary Science, Univ of Kentucky, Lexington, Kentucky 2
In mares pre-ovulatory estrogen (E2) is associated with increased uterine edema, which dissipates several days prior to ovulation. Because the pre-ovulatory follicle contains high concentrations of progesterone (P4) that are not evident in the peripheral circulation, we investigated the effects of P4 and E2 exposure on the onset and regression of uterine edema. Long-term OVX mares were given one of the following four treatments: G1: (control) 3cc sesame oil IM, G2: P4 (75mg/3cc sesame oil IM) for two days then E2 (5mg/3cc sesame oil IM), G3: E2 only (5mg/3cc sesame oil IM), or G4: E2 (5mg/3cc sesame oil IM) for one day then P4 (75mg/3cc sesame oil IM) twice daily until uterine edema dissipated completely. Uterine edema was monitored via ultrasound daily and jugular vein blood collected. On the day of E2 administration, mares were monitored via ultrasound and blood collected every 2h for 12h. Control mares showed no increase in uterine edema. G2 mares showed a rapid onset of edema approximately 4h after E2 treatment followed by a decrease in edema 8-10 h post-treatment. G3 mares exhibited increased uterine edema by 6 h post-treatment, which remained for several days. G4 mares showed an edema pattern similar to G3 mares, but the edema dissipated earlier than G3 mares following P administration. These experiments indicate that E2 and P4 are involved in the onset and regression of uterine edema. Experiment 2 was performed to examine E2 and P4 receptors (Rc.) OVX mares were given either vehicle (control) or 5mg E2 (treatment.) Uterine biopsies were collected as follows: G1 (vehicle only) at 0h, G2 at 3h post-treatment, G3 at 6h post-treatment, G4 at 9h post-treatment, or G5 at 12h post-treatment. There was no significant change in E2-Rc concentration over time. In contrast, there was a significant rise in P4-Rc at 9h post-treatment (P<0.026). We believe that the pre-ovulatory rise in E2 induces an increase in uterine edema and also upregulates the P4-Rc allowing P4 to work through these receptors to dissipate edema prior to ovulation.
Keywords: Uterus, Edema, Estrogen
This abstract is being presented at: 8:00 AM in session: