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 F production in caruncular and intercaruncular tissue have been 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 oestradiol. 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 oestradiol or progesterone treatment in intercaruncular tissue of ovariectomized ewes. beta-Glucuronidase and acid phosphatase activities and steroid metabolism were unaffected by pregnancy. However, in ovariectomized animals oestradiol treatment stimulated beta-glucuronidase activity in endometrium and myometrium. Progesterone treatment stimulated acid phosphatase activity in the intercaruncular endometrium. The results show that amongst several endometrial constituents investigated relatively few changes were detected by Day 15 post coitum, one 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 oestradiol and progesterone, and in intercaruncular tissue by oestradiol treatment only.

SUMMARY1. Arterial and mammary venous concentrations of prostaglandins F. (PGFa), E (PGE) and the PGFa metabolite, 13,14-dihydro-15-oxoPGFa (DHK-PGFe) were studied during late pregnancy and the onset of lactation in conscious goats. Mammary secretion concentrations of PGFa and DHK-PGFa were determined, and mammary blood flow, arterial plasma progesterone concentrations and milk composition were also studied.2. A significant output of PGFa from the mammary gland into mammary venous blood was observed during late pregnancy; this output ceased near term.3. Mammary output of DHK-PGFa into venous blood began about 6 days prepartum, suggesting an increasing capacity of the gland to metabolize PGFa.4. The concentration of PGFa in mammary secretion increased from about 4 days pre-partum, that of DHK-PGFa from about 12 days pre-partum.5. It is concluded that although total mammary output of PGFa decreases during late pregnancy and early lactation, the rate of mammary synthesis of PGFa increases and the PGFa is increasingly secreted into milk and metabolized to DHK-PGFe within the mammary gland.

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1 Homogenized lung tissue from day 15, pregnant and non-pregnant guinea-pig metabolized exogenous prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha) almost completely when incubated in Tyrode solution containing beta-nicotinamide adenine dinucleotide (NAD+). 2 Metabolism of PGE2 and PGF2alpha by homogenates of day 15, pregnant or non-pregnant, guinea-pig uteri was relatively low (8 to 20%) when incubated in Tyrode solution containing NAD+. 3 Day 15, guinea-pig conceptuses (placentae and embryos), homogenized and incubated in Tyrode solution containing NAD+, metabolized prostaglandins to a slightly greater extent (14 to 22%) than day 15, uterine tissue. 4 Addition of exogenous arachidonic acid to day 12 or day 15, pregnant, guinea-pig uterine homogenates in Tyrode solution did not increase the yield of PGF2alpha following incubation. 5 It is concluded that neither an increase in metabolism of PGF2alpha by the uterus and conceptus nor lack of precursor is responsible for the lower secretion of PGF2alpha from the day 15, pregnant, guinea-pig uterus when compared to the day 15, non-pregnant uterus.