Analysis of mouse uterine proteins at pro-oestrus, during early pregnancy and after administration of exogenous steroids

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Abstract
Uterine secretions were analyzed after labeling with L-[4,5-3H]leucine. During proestrus major protein peaks were seen with approximate MW 2.0 .times. 104, 2.7 .times. 104, 4.0 .times. 104, 5.7 .times. 104, 7.8 .times. 104 and 13.0 .times. 104. Qualitative changes were observed during the first 4 days of pregnancy. On day 4 p.c.[post coitum] secretions revealed 2 prominent peaks with MW 6.7 .times. 104 and 12.5 .times. 104, 4 peaks between 2.0 and 4.7 .times. 104 and 1 at 8.5 .times. 104 and 1 at 20.0 .times. 104. Profiles similar to those on day 4 p.c. and implantation, were induced in ovariectomized females by administration of exogenous progesterone and estradiol. The proteins detected after administration of exogenous estradiol alone were essentially similar to those found at proestrus. Ovariectomized mice treated with the steroid sequence to mimic day 4 p.c. profiles but not given the final injection of estradiol showed no detectable labeled proteins. Injection of progesterone or estradiol alone, in the final sequence of injections given to ovariectomized pregnant females treated with progesterone, did not induce blastocyst implantation. A synergistic relationship between progesterone and estrogen in the secretion of uterine macromolecules is indicated.