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

Abstract:
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:
Uterus/Oviduct I