RESUMEN
<p><b>OBJECTIVE</b>To evaluate the influence of superovulation by GnRHa protocol and pregnant mare's serum gonadotropin (PMSG) alone on the expression of estrogen receptor (ER), progesterone receptor (PR) and leukemia inhibitory factor (LIF) mRNA on endometrium.</p><p><b>METHODS</b>Forty-five female ICR mice were randomly allocated into 3 groups:(1) GnRHa+PMSG group: alarelin was give first for desensitizing the pituitary, then superovulation with PMSG; (2) PMSG group: mice were injected with PMSG only; (3) Natural cycle group: mice were given with same volume of saline. Endometrium samples were taken at 48 hours after given hCG or ovulation (control group). ER and PR in glandular cells were detected with SP immunohistochemistry semiquantitatively. Expression of LIF mRNA on endometrium was detected with reverse transcriptase-polymerase chain reaction (RT-PCR) analysis.</p><p><b>RESULT</b>The positive rate(%) and expression intense (AU) of ER and PR on glandular epithelium cells were significantly lower in GnRHa+PMSG group and PMSG group than those in natural cycle group (all P <0.01). The expression of LIF mRNA was significantly lower in GnRHa+PMSG group and PMSG group than that in natural cycle group (all P <0.01); but the expressions of ER, PR and LIF in GnRHa+PMSG group were higher than those in PMSG group.</p><p><b>CONCLUSION</b>The protocol with GnRHa down regulates the expressions of ER, PR and the LIF mRNA on the mice of secretive phase endometrium, suggesting it may have an adverse effect on the endometrial receptivity in mice, but it may still be better than PMSG alone.</p>