Protein, prostaglandin and steroid synthesis in caruncular and intercaruncular endometrium of sheep before implantation

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Abstract
The effect of the presence of a preimplantation embryo on protein concentration, rate of protein synthesis, .beta.-glucuronidase and acid phosphatase activities, steroid metabolism and prostaglandin [PG]F production in caruncular and intercaruncular tissue was studied for sheep at day 15 of pregnancy. The rate of protein synthesis in both tissues was greater in pregnant than in non-pregnant animals, although the difference was only significant in caruncular endometrium. The effect in caruncular tissue was mimicked in ovariectomized animals treated with estradiol. Localized changes in the caruncular tissue were observed in respect of PGF with an increased tissue concentration, an enhanced basal release when the tissue was incubated in the presence of indomethacin and a decreased net production. Maximum production of PGF in the 2 tissues was unaffected by the presence of an embryo but it was enhanced by estradiol or progesterone treatment in intercaruncular tissue of ovariectomized ewes. .beta.-Glucuronidase and acid phosphatase activities and steroid metabolism were unaffected by pregnancy. In ovariectomized animals estradiol treatment stimulated .beta.-glucuronidase activity in endometrium and myometrium. Progesterone treatment stimulated acid phosphatase activity in the intercaruncular endometrium. Amongst several endometrial constituents investigated relatively few changes were detected by day 5 post-coitum, 1 day before definitive attachment. Those changes that did occur were associated with the dynamics of PGF production and the rate of protein synthesis, and were consistent with the production of a PGF binding component in caruncular endometrium which may be concerned with the protection of luteal function by redirection of uterine PGF production. Canonical variate analysis revealed that changes on day 15 of pregnancy were mimicked most closely in caruncular tissue by treatment of ovariectomized ewes with estradiol and progesterone, and in intercaruncular tissue by estradiol treatment only.