Role of estradiol and progesterone in regulating prostaglandin F(2 alpha) secretion and luteolysis in the ewe

Three studies were conducted to evaluate the effects of estradiol and progesterone on the secretory pattern of oxytocin and the oxytocin-induced secretion of prostaglandin F\sb{2α} (PGF\sb{2α}) during luteolysis in the ewe. For the first two studies, fifty mixed-breed ewes underwent selective irradiation of both ovaries on day 8 of the cycle to destroy the estrogen-secreting follicles. Twenty ewes were randomly assigned to four treatment groups in study 1. These groups included the presence and absence of estradiol and the presence and absence of onapristone, a progesterone-receptor antagonist. The remaining thirty ewes were randomly assigned to six treatment groups in study 2. These groups included the presence and absence of onapristone over days 13, 14 and 15. Simultaneous samples were collected at 7.5-minute intervals from the jugular vein, carotid artery and vena cava on day 13 (study 1) or day 13, 14 or 15 (study 2) for determination of oxytocin and PGF\sb{2α} concentrations. At the completion of sampling, ewes were euthanized and their uteri collected for determination of oxytocin receptor concentrations and oxytocin-induced phosphatidylinositide formation and hydrolysis. In the third study, twenty ewes which had been ovariectomized on day 12 of the cycle, were randomly assigned to four treatment groups. These groups included the presence and absence of estradiol and the presence and absence of progesterone. On day 15, samples were collected at 5-minute intervals from the jugular vein for determination of oxytocin and 13, 14-dihydro-15-keto-prostaglandin F\sb{2α} (PGFM) concentrations. At the completion of sampling, 1 μg oxytocin was administered and jugular samples were collected for determination of oxytocin-induced PGFM secretion. Ewes were then euthanized and the uteri collected for determination of receptor concentrations.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Veterinary Biosciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Walker, Douglas Lee

Contributors dc:contributor

• Hixon, James E.

• Biology, Animal Physiology
• Biology, Veterinary Science

Statement dc:rights

• Copyright 1995 Walker, Douglas Lee

Language dc:language

eng

Identifier

AAI9624526
(UMI)AAI9624526

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20803