Expression of Estrogen Receptor Subtypes in Rat Pituitary Gland during Pregnancy and Lactation

Abstract

The aim of this study was to examine whether the expression levels of mRNA of the three estrogen receptor (ER) subtypes, ERalpha, ERbeta, and truncated ER product-1 (TERP-1) found in the rat pituitary gland were modified during gestation, lactation, and postlactation periods. By using relative quantitative RT-PCR, we found that ERalpha mRNA significantly peaked in midpregnancy. However, the ERalpha protein level remained constant. ERbeta gene expression did not change throughout pregnancy, suggesting that it was not related to estradiol levels during this reproductive period. In contrast, both TERP-1 mRNA and protein levels dramatically increased throughout the second half of gestation, being faintly detectable in early pregnancy. TERP-1 expression was rapidly reversed by lactation, whereas neither pituitary ERalpha nor ERbeta relative levels were significantly altered. In addition, pup removal for 24-96 h on d 9 postpartum significantly reduced the expression of both ERalpha and ERbeta mRNA compared with that in lactating animals, but the expression of TERP-1 mRNA was no longer detected. Collectively, our data indicate that 1) TERP-1, ERalpha, and ERbeta expression levels are differentially regulated in the pituitary; 2) TERP-1 is variably expressed depending on the hormonal environment related to the estrous cycle, pregnancy, and lactation; and 3) TERP-1/ERalpha ratios dramatically change depending on reproductive periods, suggesting a critical role for TERP-1 in reproductive events.

Chicken RFamide-related Peptide (GnIH) and Two Distinct Receptor Subtypes: Identification, Molecular Characterization, and Evolutionary Considerations

“…An activation of inhibitory pathways may modulate the steady-state levels of Gαi2 mRNA [27,28]. The relative expression levels of Gα i2 mRNA were semiquantified by RT-PCR with Gi2-S (TCAAACTTAC-TCTGGATGTAGCTG) and Gi2-A (TCAAACTTA-CTCTGGATGTAGCTG), as described elsewhere [29,31]. The reaction condition was as follows: 94 C for 5 min followed by 23 cycles of 94 C for 40 sec, 61 C for 25 sec, and 72 C for 35 sec.…”

The integrated action of oestrogen receptor isoforms and sites with progesterone receptor in the gonadotrope modulates LH secretion: evidence from tamoxifen-treated ovariectomized rats

“…Rat gonadotropes express both isoforms of ER, the predominant ERa (Lindzey et al 2006) and ERb at nuclear level (Kuiper et al 1997, Mitchner et al 1998, Vaillant et al 2002, Sánchez-Criado et al 2005a. In addition, an ER which appears to be the same protein as nuclear ERa is expressed at the plasma membrane level (Bression et al 1986, Razandi et al 1999, Toran-Allerand et al 1999, Schmidt et al 2000, Kelly & Levin 2001, Simoncini & Genazzani 2003, Toran-Allerand 2004, Levin 2005.…”

Truncated Estrogen Receptor Product-1 Stimulates Estrogen Receptor α Transcriptional Activity by Titration of Repressor Proteins

“…In vitro translated TERP is detected as a pair of doublets at 22-24 kDa, which likely represent translation from two methionines, at amino acids 393 and 408 in exon 5 (28,32). The larger protein is detected preferentially in transfected cells and in normal pituitaries (11,28,29,31,32). The dimerization mutants of ER␣ and TERP, ER␣ L509R and TERP L509R, also interact with GST-REA in a similar fashion (Fig.…”

“…However, we found that REA mRNA expression varies less than 2-fold throughout the estrous cycle and is similar to that of ER␣ (data not shown). In contrast, TERP expression changes dramatically in response to E 2 (26,31), during pregnancy (29), and throughout the estrous cycle (Fig. 5B).…”

“…Levels of TERP mRNA change dramatically in response to estrogen (10,29,30), and it seems likely that TERP may have biological importance in the pituitary (31). TERP is transcribed from a promoter located in the intron between exons 4 and 5 of the rat ER␣ gene (32).…”