In addition to key mammotrophic hormones such as the pituitary prolactin (PRL) and the ovarian steroids progesterone and estradiol, there are local factors that modulate the tissue dynamics of the mammary glands during pregnancy and lactation. By immunohistochemistry and RT-PCR, we found local transcription and translation of gonadotropin-releasing hormone (GNRH), GNRH receptor (GNRHR), PRL and PRL receptor (PRLR) in mammary glands of adult vizcachas during pregnancy and lactation. Both GNRH and GNRHR showed a lag between protein expression and gene transcription throughout the gestational period: while the highest transcription levels of these genes were recorded at early-pregnancy, the epithelial immunoexpressions of both showed their maximum during lactation. RIA results corroborated the presence of GNRH in mammary glands at all the analyzed stages and confirmed the maximum amount of this peptide in the lactating group. Significant amounts of GNRH were detected in milk samples as well. Conversely, PRL and PRLR shared similar protein and gene expression profiles, all exhibiting maximum values during lactation. GNRH peptide content in mammary glands of females with sulpiride-induced hyperprolactinemia (HP) was significantly lower than that of control females (CT). Although PRL mRNA levels remained unchanged, there was a marked increase in the α-lactalbumin (LALBA) transcription in mammary glands of HP- vs CT-females. These results suggest that after targeting mammary glands, PRL stimulates the expression of milk protein genes, but also, tempers the local expression of GNRH. Mammary gland-explants supplemented with a GNRH analogue (GN-explants) had no differences in terms of PRLR or LALBA transcription levels compared to CT-explants, so the mammary PRLR signaling would not appear to be modulated by GNRH. Yet, mRNA expression levels of both GNRH and the GNRHR-downstream factor, EGR1, were significantly higher in GN-explants compared to that of CT which would point to a GNRH-positive feedback mechanism. In summary, the local coupled expression of GNRH, GNRHR and EGR1 in the mammary gland throughout pregnancy of vizcachas, the PRL-dependent mammary GNRH secretion as well as the GNRH positive feedback on its own transcription suggest an autocrine-paracrine regulatory mechanism and propose an active role for GNRH in mammary gland tissue remodeling.

除了诸如垂体催乳激素（PRL）和卵巢类固醇孕激素和雌二醇等主要的乳腺营养激素外，还有一些局部因素可调节妊娠和哺乳期乳腺的组织动力学。通过免疫组织化学和RT-PCR，我们发现在成年比斯加查人的乳腺在怀孕和哺乳期间，促性腺激素释放激素（GNRH），GNRH受体（GNRHR），PRL和PRL受体（PRLR）的局部转录和翻译。GNRH和GNRHR在整个妊娠期均显示蛋白质表达和基因转录之间存在滞后：虽然这些基因的最高转录水平在妊娠早期记录，但两者的上皮免疫表达均在哺乳期达到最高。RIA结果证实了在所有分析阶段乳腺中GNRH的存在，并证实了泌乳组中该肽的最大量。在牛奶样品中也检测到大量的GNRH。相反，PRL和PRLR具有相似的蛋白质和基因表达谱，在泌乳期均表现出最大值。舒必利引起的高泌乳素血症（HP）的女性乳腺中的GNRH肽含量显着低于对照女性（CT）。尽管PRL mRNA的水平保持不变，但HP雌性与CT雌性的乳腺中α-乳清蛋白（LALBA）转录显着增加。这些结果表明，在靶向乳腺后，PRL刺激了乳蛋白基因的表达，而且还调节了GNRH的局部表达。与CT外植体相比，补充了GNRH类似物的乳腺外植体（GN外植体）在PRLR或LALBA转录水平方面没有差异，因此乳腺PRLR信号传导似乎不会受到GNRH的调节。然而，与CT相比，GN外植体中GNRH和GNRHR下游因子EGR1的mRNA表达水平显着更高，这表明CT的表达是GNRH阳性反馈机制。综上所述，整个粘液妊娠期间，乳腺中GNRH，GNRHR和EGR1在乳腺中的局部偶联表达，PRL依赖性乳腺GNRH分泌以及其自身转录的GNRH阳性反馈提示自分泌-旁分泌调节机制，并提出了一个建议。 GNRH在乳腺组织重塑中的积极作用。