Sahlin Lena, Masironi Britt, Akerberg Sonja, Eriksson Håkan
Division for Reproductive Endocrinology, Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Reprod Biol Endocrinol. 2006 Sep 11;4:47. doi: 10.1186/1477-7827-4-47.
Estradiol (E2) and progesterone (P) are well known regulators of progesterone receptor (PR) expression in the rat uterus. However, it is not known which receptor subtypes are involved. Little knowledge exist about possible differences in PR regulation through ERalpha or ERbeta, and whether the PR subtypes are differently regulated depending on ER type bound. Thus, in the present study PR immunostaining has been examined in uteri of ovariectomized (ovx) rats after different treatments of estrogen and P, in comparison with that in immature, cycling, and pregnant animals.
The uteri were collected from 1) ovx rats treated with E2 and/or P; 2) immature rats, intact cycling rats and animals pregnant day 8 and 18; 3) ovx rats treated with E2 or an estrogen receptor (ER)alpha agonist or an ERbeta agonist. Two antibodies were used, one detecting PRA+B and another one specific for PRB. Real-time PCR was used to determine mRNA levels for PRAB and PRB in experiment 3.
In stroma and myometrium faint staining was detected in ovx controls (OvxC), whereas E2 treatment resulted in strong staining. In contrast to this, in luminal epithelium (LE) the staining was strong in the OvxC group, whereas E2 treatment during the last 24 hrs before sacrifice caused a decrease. Similar to OvxC the LE of the immature animals was strongly stained. In the pregnant rats LE was negative, well in agreement with the results seen after E2 treatment. In the pregnant animals the stroma and decidua was strongly stained for PRAB, but only faint for PRB, indicating that PRA is the most expressed isoform in this state. The increase in stromal and myometrial immunostaining after E2 treatment was also found after treatment with the ERalpha agonist PPT. The ERbeta agonist DPN caused a decrease of the PR mRNA levels, which was also found for PRAB and PRB immunostaining in the GE.
Stromal and myometrial PRAB levels are increased via ERalpha, as shown by treatment with E2 and the ERalpha agonist PPT, while the levels in LE are decreased. The uterine stroma of pregnant rats strongly expressed PRAB, but very little PRB, which is different to E2 treated ovx animals where both PRAB and PRB are strongly expressed. The ERbeta agonist DPN decreased the mRNA levels of PRAB and PRB, as well as the PRAB protein level in GE. These results suggest that ERbeta signals mainly down-regulate PR levels in the epithelial cells. ERalpha, on the other hand, up-regulates PR levels in the stroma and myometrium while it decreased them in LE. Thus, the effects from E2 and PPT on the mRNA levels, as determined by PCR, could be annihilated since they are increased and decreased depending on cell type. The distribution and amount of PR isoforms strongly depend on the hormonal milieu and cell type within the rat uterus.
雌二醇（E2）和孕酮（P）是大鼠子宫中孕酮受体（PR）表达的知名调节因子。然而，尚不清楚涉及哪些受体亚型。关于通过雌激素受体α（ERα）或雌激素受体β（ERβ）对PR调节的可能差异，以及PR亚型是否根据结合的ER类型而受到不同调节，了解甚少。因此，在本研究中，与未成熟、处于发情周期和怀孕动物相比，对去卵巢（ovx）大鼠子宫进行不同雌激素和P处理后，检测了PR免疫染色情况。
子宫取自1）用E2和/或P处理的ovx大鼠；2）未成熟大鼠、完整发情周期大鼠以及妊娠第8天和第18天的动物；3）用E2或雌激素受体（ER）α激动剂或ERβ激动剂处理的ovx大鼠。使用了两种抗体，一种检测PRA+B，另一种对PRB具有特异性。在实验3中，使用实时PCR来测定PRAB和PRB的mRNA水平。
在ovx对照组（OvxC）的基质和肌层中检测到微弱染色，而E2处理导致强染色。与此相反，在腔上皮（LE）中，OvxC组染色强，而在处死前最后24小时进行E2处理则导致染色减少。与OvxC组类似，未成熟动物的LE染色强。在怀孕大鼠中，LE为阴性，这与E2处理后的结果一致。在怀孕动物中，基质和蜕膜PRAB染色强，但PRB仅微弱染色，表明PRA是该状态下表达最多的异构体。用ERα激动剂PPT处理后，也发现E2处理后基质和肌层免疫染色增加。ERβ激动剂DPN导致PR mRNA水平降低，在腺上皮（GE）中PRAB和PRB免疫染色也出现这种情况。
如用E2和ERα激动剂PPT处理所示，通过ERα可使基质和肌层PRAB水平升高，而LE中的水平降低。怀孕大鼠的子宫基质强烈表达PRAB，但PRB极少，这与E2处理的ovx动物不同，后者PRAB和PRB均强烈表达。ERβ激动剂DPN降低了PRAB和PRB的mRNA水平以及GE中的PRAB蛋白水平。这些结果表明，ERβ信号主要下调上皮细胞中的PR水平。另一方面，ERα上调基质和肌层中的PR水平，同时降低LE中的PR水平。因此，PCR测定的E2和PPT对mRNA水平的影响可能会相互抵消，因为它们根据细胞类型而升高和降低。PR异构体 的分布和数量强烈依赖于大鼠子宫内的激素环境和细胞类型。
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