Synthesis of Uterine E#{241}dometrial Proteins during Early Diestrus in the Cyclic and Pregnant Dog, and after Estrogen and Progesterone Treatment1

The objectives of this study were to identify and characterize dog uterine endometrial proteins synthesized de novo in explant culture during early luteal phase, to examine distribution of these proteins prior to the embryo’s entering the uterus and during its free-floating period prior to implantation, and to examine regulation of endometrial proteins by estrogen and progesterone (P4) treatments. Uterine endometrium was collected from cyclic and pregnant bitches on diestrus Days 3, 7, and 10 as determined by loss of cornlflcation of vaginal epitheium, and from ovariectomized dogs after treatment with corn oil, estrogen, F,, or estrogen followed by 1 or 2 wk of P4. Tissue was incubated in an explant culture system in the presence of l3HIleucme or [35SJmethionine. The rate of incorporation of [3Hlleucine into nondialyzable macromolecules indicated no significant change in rates of incor- poration by status (pregnant vs. nonpregnant), day, or steroid treatment. Uterine endometrial-conditioned culture medium, ana- lyzed by two-dimensional SDS-PAGE and fluorography, revealed a complex array of at appears different by day but not by status, suggesting that the preimplantation embryo does not have an effect on uterine endometrial protein synthesis and secretion. Expression of specific proteins during early diestrus, however, appears to be in response to specific regimens of estrogen and P4 that mimic spontaneous early diestrus.