The time between ovariectomy and initiation of the hormone treatments (6 days) should have been sufficient for steroid-dependent mRNA levels to decline. The apparent lack of LIF mRNA down-regulation after ovariectomy, together with the absence of any inducement or inhibition of LIF expression by steroid treatments in comparison with values in the ovariectomized controls, suggests that uterine LIF is not regulated by either progesterone or estradiol. However, we did not examine uterine LIF expression at varying time points throughout any of the hormone treatments. Therefore, we cannot rule out the possibility of a transient change in LIF mRNA abundance in response to these steroids or PRL. Yet the process of blastocyst activation occurs over several days, and uterine LIF mRNA appears to remain elevated for several days throughout this period. Therefore, it is likely that continuous administration of the appropriate compound would induce a prolonged rather than transient increase in mRNA concentration in the uterus. Buy Advair Diskus Online
Mean uterine LIF mRNA concentration in ovariecto-mized (control) skunks was about 1.7 times greater than that in intact animals with blastocysts in diapause. The difference between the means of these two groups approached statistical significance (p = 0.059). Since these results were obtained in separate assays, it is possible that interassay variation might have obscured a physiological effect of ovariectomy, which in turn may have hindered our ability to detect an effect of one or more of the steroid treatments on LIF abundance. If one assumes the latter to be true, one would interpret the results as indicating that ovariectomy induced an increase in uterine LIF concentration. It should also be noted that LIF expression in uteri of ovariectomized or ovariectomized steroid-treated skunks was only slightly lower and that it did not significantly differ from the level observed in pregnant females whose uteri contained early activated blastocysts.