Interleukin-1, tumor necrosis factor, platelet-derived growth factor, transforming growth factor (3, and EGF alter LIF expression in the human uterus. EGF-R mRNA and EGF-induced protein tyrosine kinase activity increase at the time of renewed embryonic development. EGF treatment of skunks with delayed implanting blastocysts seemingly elevated uterine LIF mRNA concentrations to values equivalent to those observed in intact skunks with activated blastocysts. However, the small sample size and disparate LIF/cyclophilin ratios (0.24, 0.13, 0.07) prevent one from drawing conclusions from this result. Moreover, prolonged infusion of intact pregnant skunks with EGF failed to induce blastocyst activation or implantation. Cheap Diskus Advair
Data presented in this study suggest a relationship between uterine LIF expression, embryo development, and implantation in the skunk that is consistent with that observed in the mouse, rabbit, mink, and human. However, the essentiality of LIF in implantation has been directly demonstrated only in the mouse. Constant infusion of recombinant mouse LIF at a rate of 790 pg/min per milliliter (assuming an average body weight of 30 g and blood volume of 2.1 ml) for 72 h resulted in embryo implantation in LIF female mice and induced cachexia, which suggests that the dose used was pharmacological. Preliminary experiments involving constant infusion of rhLIF (120 pg/min per milliliter; average body weight of 370 g and assumed blood volume of 28 ml) into intact skunks with delayed implanting blastocysts for 7 days failed to increase uterine weight or blastocyst diameter or to induce implantation or cachexia.