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Biology of Reproduction, Vol 13, 587-596, Copyright © 1975 by Society for the Study of Reproduction
1 Worcester Foundation for Experimental Biology,
Shrewsbury, Massachusetts 01545 The role of 17 Using the optimal conditions for prostaglandin biosynthesis as determined in the first part of
this experiment (i.e.: 2 days of progesterone pretreatment and uterine cannulation 12 h after
estradiol administration), the effect of estradiol doses between 0.001 and 100 µg was investigated.
Maximum UVP levels of PGE and PGF were obtained with doses greater than 1.0 µg estradiol. The
simultaneous administration of progesterone (2, 10 or 50 mg) with estradiol (10 µg) significantly
reduced PGF concentration in UVP, whereas only 50 mg progesterone was effective in significantly
reducing PGE levels. Fifty mg of progesterone alone was without effect on PGE and PGF levels in
UVP. It is concluded that estrogens are the predominant ovarian steroids involved in the regulation of
uterine prostaglandin biosynthesis in the rat; however, important roles for progesterone in the
expression of estradiol stimulated activity are indicated.
-estradiol and progesterone in the in vivo synthesis of prostaglandins by the
ovariectomized rat uterus was investigated. Seven days after ovariectomy, rats were treated with
progesterone (2 mg x 2 days) then given a single injection of estradiol. Prostaglandin E (PGE) and
F (PGF) were determined by RIA in uterine tissue and uterine vein plasma (UVP) at 0, 0.5, 1, 2, 4,
8, 12 and 24 h after the administration of 17-estradiol (10 µg). PGF and PGE content (ng/uterus)
remains constant from the time of estradiol administration to the latest time period studied. PGF
and PGE concentrations (ng/100 mg uterine wt) show a gradual decline during the course of
estrogen action which becomes significant only 12 and 24 h after estradiol administration and is
correlated with the increase in uterine weight. Following progesterone administration, there is a
significant increase in both uterine PGE content and concentration from ovariectomized levels.
These results indicate that levels measured in UVP represent a true de novo synthesis of
prostaglandins and could not be accounted for by the release of stored material into the uterine
vein. PGF levels in UVP rose from control values of 2.42 ± 0.53 ng/ml to a maximum of 23.30 ±
4.96 ng/ml at 12 h and by 24 h had returned to basal levels. A comparison with animals not treated
with progesterone revealed low levels of PGF in UVP at all time periods studied (0.5-12 h). PGE
levels in UVP after estradiol administration to progesterone-treated and untreated rats were similar,
although at 12 h, levels in progesterone-treated rats were significantly greater than the untreated
group. Determinations of estradiol in peripheral plasma by RIA revealed a sharp peak 1 h after administration followed by a rapid decline to control values by 12 h.
Accepted on September 16, 1975
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