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

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Title: Role of estradiol and progesterone in regulating prostaglandin F(2 alpha) secretion and luteolysis in the ewe
Author(s): Walker, Douglas Lee
Doctoral Committee Chair(s): Hixon, James E.
Department / Program: Veterinary Biosciences
Discipline: Veterinary Biosciences
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Biology, Animal Physiology Biology, Veterinary Science
Abstract: 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$\sb{2\alpha}$ (PGF$\sb{2\alpha}$) 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$\sb{2\alpha}$ 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$\sb{2\alpha}$ (PGFM) concentrations. At the completion of sampling, 1 $\mu$g 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.These studies suggest that oxytocin is not the only oscillator responsible for regulating pulsatile PGF$\sb{2\alpha}$ secretion at the time of luteolysis as evidenced by the findings that: (1) 50% or more of the PGF$\sb{2\alpha}$ pulses were not preceded by or coincident with an oxytocin pulse, (2) changes in the number, amplitude or duration of PGF$\sb{2\alpha}$ pulses did not reflect similar changes in the secretion of oxytocin, (3) changes in uterine oxytocin receptor concentrations were not correlated with PGF$\sb{2\alpha}$ secretion or oxytocin-induced PGFM secretion but were correlated with the oxytocin-induced hydrolysis of $\sp3$H-phosphatidylinositides, even though the oxytocin-induced formation of $\sp3$H-inositol monophosphate was not correlated with either the number or amplitude of PGF$\sb{2\alpha}$ pulses and (4) a pulsatile pattern in the secretion of PGF$\sb{2\alpha}$ was observed in ovariectomized ewes under conditions where the administration of oxytocin failed to influence PGF$\sb{2\alpha}$ synthesis and secretion.
Issue Date: 1995
Type: Text
Language: English
URI: http://hdl.handle.net/2142/20803
Rights Information: Copyright 1995 Walker, Douglas Lee
Date Available in IDEALS: 2011-05-07
Identifier in Online Catalog: AAI9624526
OCLC Identifier: (UMI)AAI9624526
 

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