Differential effects of progesterone treatment on the oxytocin-induced prostaglandin F2 alpha response and the levels of endometrial oxytocin receptors in ovariectomized ewes

• Published in: Biology of reproduction Vol. 46; no. 1; pp. 17 - 22
• Main Authors: Lau, T.M. (Vicotrian Institute of Animal Science, Werribee, Vicotria, Australia), Gow, C.B, Fairclough, R.J
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.01.1992
• Subjects: Animals; Biological and medical sciences; BREBIS; Dinoprost - metabolism; Endometrium - drug effects; Endometrium - physiology; Female; FEMELLE; Fundamental and applied biological sciences. Psychology; HEMBRA; Hormone metabolism and regulation; Kinetics; Mammalian female genital system; OCYTOCINE; OVARIECTOMIA; OVARIECTOMIE; Ovariectomy; OVEJA; OXITOCINA; Oxytocin - pharmacology; PROGESTERONA; PROGESTERONE; Progesterone - blood; Progesterone - pharmacology; PROSTAGLANDINAS; PROSTAGLANDINE; Receptors, Angiotensin - drug effects; Receptors, Angiotensin - metabolism; Receptors, Oxytocin; Sheep; UTERO; UTERUS; Vertebrates: reproduction; Oxytocin; Ovariectomy; Arachidonic acid derivatives; Neuropeptide; Prostaglandin F2α; Vertebrata; Mammalia; Uterus; Female genital system; Hormonal regulation; Sheep; Artiodactyla; Progesterone; Ungulata; Endometrium; Hormonal receptor
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod46.1.17

The oxytocin-induced uterine prostaglandin (PG) F(2 alpha) response and the levels of endometrial oxytocin receptors were measured in ovariectomized ewes after they had been given steroid pretreatment (SP) with progesterone and estrogen to induce estrus (day of expected estrus = Day 0) and had subsequently been treated with progesterone over Days 1-12 and/or PGF(2 alpha) over Days 10-12 postestrus. The uterine PGF(2 alpha) response was measured after an i.v. injection of 10 IU oxytocin on Days 13 and 14, using the PGF(2 alpha) metabolite, 13,14-dihydro-15-keto-PGF(2 alpha) (PGFM), as an indicator for PGF(2 alpha) release. The levels of oxytocin receptors in the endometrium were measured on Day 14. During the treatment with progesterone, the peripheral progesterone concentrations were elevated and remained above 1.8 ng/ml until the morning of Day 14. The PGFM responses to oxytocin untreated controls and SP controls were low on both Days 13 and 14 whereas the levels of endometrial oxytocin receptors in the same ewes were high. Treatment with progesterone either alone or in combination with PGF(2 alpha) significantly (p 0.04) increased the PGFM response on Day 14 and reduced the levels of endometrial oxytocin receptors; treatment with PGF(2 alpha) alone had no effect. It is concluded that progesterone promotes the PGFM response to oxytocin while simultaneously suppressing the levels of endometrial oxytocin receptors. PGF(2 alpha) treatment had no effect on either the uterine secretory response to oxytocin or the levels of oxytocin receptors in the endometrium. The results also confirm a previous report indicating that in chronically ovariectomized and steroid-treated ewes there was no apparent direct correlation between oxytocin receptor levels and the uterine PGF response to an oxytocin stimulus