Expression of the progesterone receptor, bcl-2 and bax in clomiphene citrate treated rat uteri
Date
2011-06-02
Authors
Dix-Peek, Therese
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Abstract
Clomiphene citrate (CC) is a synthetic oestrogen receptor modulator that may act
to promote or inhibit oestrogenic responses depending on the type of tissue or
organism. CC acts as a superovulator and has been widely prescribed in the
treatment of female infertility. However, pregnancy rates after CC treatment are
low, possibly due to the CC causing morphological and other unidentified changes
to the uterus.
This study investigated the changes caused by CC on the progesterone receptor
(PR), the anti-apoptotic protein, Bcl-2, and the pro-apoptotic protein, Bax.
PR with its ligand, progesterone, is important for the maintenance of a pregnancy.
Bcl-2 is a cell survival molecule and acts in opposition to Bax, which promotes
apoptosis, which is important in allowing an attaching blastocyst to infiltrate the
maternal endometrium.
A high physiological dose of CC (1.25 mg) was administered to ovariectomised
rats, either as a single treatment, or prior to a hormonal treatment regime
characteristic of pre-implantation animals. The single CC treated animals were
compared with single 5 mg progesterone (P4) treated animals and vehicle controls.
The animals treated with CC in conjunction with the ovarian hormone milieu
(CCPPPE treatment) were compared to PPPE treated animals or to the vehicle
controls.
The effects of CC, P4, PPPE and SPPPE on the morphology of the uteri were
investigated by light microscopy. Expression of the PR, Bcl-2 and Bax were
investigated using immunohistochemistry and enzyme linked immunosorbent
(ELISA) techniques.
The present study showed that CC treatment affects the microanatomy of the
uterine compartments, particularly the shape of the lumen and the luminal
epithelial height. The expressions of PR, Bcl-2 and Bax in the entire uterus were not significantly affected by the various treatments applied to the ovariectomised
rats, as measured using ELISA. However, expression of the proteins in the various
uterine compartments was altered by CC treatment. The single CC and CCPPPE
treatments had an oestrogenic effect with regards to PR expression in the uteri as
seen in the immunolocalisation, whereas the single P4 treatment decreased the PR
expression, as expected. CC treatment caused patchiness in both Bcl-2 and Bax
expression surrounding the endometrial lumen. Moreover, treatment with CC
maintained expression of Bcl-2 in the luminal epithelium, whereas the expression
of Bax shifted away from the luminal epithelium. This suggests that CC treatment
promotes cell survival of the luminal epithelium, which may diminish the ability
of the blastocyst to infiltrate the maternal tissue.
CC action is both dose sensitive and has a cumulative effect with multiple
treatments. Future studies would aim to separate the various uterine compartments
in order to quantitatively assess the actions of CC on expression in the PR, Bcl-2
and Bax. In addition, it would be interesting to investigate how the accumulation
of subsequent CC doses affects the expression of apoptotic markers, as this would
be a more realistic model for human infertility treatment.