Changes in uterine expression of leukemia inhibitory factor receptor gene during pregnancy and its up-regulation by prolactin in the western spotted skunk

The multifunctional cytokine leukemia inhibitory factor (LIF) is presumed to participate in preparing the uterus for blastocyst implantation. Increased production of LIF is positively correlated with termination of embryonic diapause and preparation for implantation in the spotted skunk, This study examined changes in the expression, localization, and hormonal regulation of LIF receptor (LIFR beta) gene expression in the uterus of the skunk. Changes in the uterine concentration of LIFR beta mRNA during pregnancy or in response to hormones after ovariectomy were determined by Northern hybridization analysis and reverse-transcriptase polymerase chain reaction. The skunk uterus produces two LIFR beta transcripts, the levels of which increase in concentration when the blastocysts resume their development but then decline somewhat during the latter stage of blastocyst activation. Ovariectomy significantly reduced uterine LIFR beta expression. Estradiol and/or progesterone failed to significantly elevate LIFR beta mRNA levels in ovariectomized animals. Prolactin significantly increased uterine concentrations of LIFR beta mRNA to greater than those of ovariectomized controls, but these levels were not comparable to those observed during preimplantation. The LIFR beta mRNA was predominately localized to stromal cells surrounding the uterine glands and in yolk sac endoderm, syncytiotrophoblast, and cytotrophoblast of postimplantation embryos.