Abstract: 83

CHANGE IN TRANSCRIPTS FOR THE PROSTAGLANDIN E₂ RECEPTOR SUBTYPES WITHIN THE PSEUDOPREGNANT RAT ENDOMETRIUM.

Karen D. Papay¹ , Thomas G. Kennedy^{1 *}
Departments of Physiology and Obstetrics and Gynaecology, The University of Western Ontario, London, ON, Canada. ¹

Prostaglandin E₂ (PGE₂) plays a role in implantation and the decidual cell reaction (DCR) of the rodent uterus, however the exact cellular cites of its action within the rat uterus are unknown. Endometrium was obtained from ovariectomized rats treated with estradiol (E₂) and progesterone in combinations to mimic pseudopregnancy (PP) (day 1-10) or to differentially sensitize uteri for the DCR. A bilateral intra-uterine injection of 0.2 ml of sesame oil was given to some rats on noon of day 5 as a deciduogenic stimulus (S) while other rats remained non-stimulated (NS). Northern blot analyses detected transcripts for all four E-prostanoid (EP) receptors within the endometrium during days 1-5. EP₂ and EP₃ mRNA steady-state levels increased to a maximum on day 5 while EP₁ and EP₄ transcript levels were unchanged. Following a deciduogenic stimulus all four EP receptors decreased to almost non-detectable levels, except for EP₂ (day 6S) and EP₁ (day 8-10S), while in NS horns all EP receptors remained elevated from days 6-10. Northern blot analyses also revealed that the increases in EP₂ and EP₃ mRNA levels on day 5 were dependent upon the dose of E₂ given on day 4, being maximal when the optimal dose of E₂ induced sensitization on day 5. In conclusion, the up-regulation of EP₂ and EP₃ genes on day 5 of PP, when the uterus is maximally sensitized for the DCR, supports previous evidence of a role for PGE₂ in the process of implantation and decidualization in the rat. Supported by the Medical Research Council of Canada.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.