Expression of Estrogen Receptor β in Rat Bone.
Expression of Estrogen Receptor β in Rat Bone.
复制标题
雌激素受体β在大鼠骨中的表达。
作者：
Y. Onoe;C. Miyaura;H. Ohta;S. Nozawa;T. Suda
最近从大鼠前列腺cDNA文库中克隆了一种新的雌激素受体，雌激素受体β（ER β）。骨是雌激素的重要靶组织，据报道ER α优先存在于成骨细胞中，但雌激素在骨中的作用机制仍不清楚。在本研究中，我们研究了ER β mRNA在骨中的表达。ER β mRNA在1日龄大鼠颅骨原代成骨细胞和大鼠骨肉瘤细胞（ROS 17/2.8）中表达明显，且表达水平高于ER α mRNA。当成骨细胞培养28天以诱导分化为能够形成骨结节的成熟成骨细胞时，ER β mRNA在整个培养期间持续高表达。相反，ER α mRNA的水平在培养开始时非常低，并在成骨细胞分化过程中逐渐增加。从8周龄的两种性别的大鼠中分离包括骨在内的各种组织，提取总RNA以比较ER β mRNA表达水平的组织分布。在股骨远端干骺端和腰椎松质骨中ER β mRNA表达明显，其水平与子宫和睾丸相当，但低于卵巢和前列腺。股骨皮质骨ER β mRNA表达水平低于松质骨。雌、雄大鼠骨中ER β mRNA的分布和表达水平无明显差异。这些结果表明，ER β mRNA在大鼠骨成骨细胞中高度表达，提示骨中ER β介导的雌激素作用存在独特的机制。
A novel estrogen receptor, estrogen receptor beta (ERbeta), has recently been cloned from a rat prostate cDNA library. In bone, which is an important target tissue of estrogen, ER alpha has been reported to be present preferentially in osteoblasts, but the mechanism of action of estrogen in bone is still not known. In the present study, we examined expression of ERbeta mRNA in bone. Expression of ERbeta mRNA was evident in primary osteoblastic cells isolated from 1-day-old rat calvaria and rat osteosarcoma cells (ROS 17/2.8), and its level was higher than that of ER alpha mRNA. When osteoblastic cells were cultured for 28 days to induce differentiation into mature osteoblasts capable of forming bone nodules, ERbeta mRNA was constantly and highly expressed during the entire culture period. In contrast, the level of ER alpha mRNA was very low at the beginning of culture and it gradually increased during the differentiation of osteoblastic cells. Various tissues including bone were isolated from 8-week-old rats of both sexes, and total RNA was extracted to compare the tissue distribution of expression levels of ERbeta mRNA. In cancellous bone of the distal femoral metaphysis and lumbar vertebra, expression of ERbeta mRNA was obvious, and its level was equivalent to those in the uterus and testis, but lower than those in the ovary and prostate. The level of ERbeta mRNA in femoral cortical bone was lower than that in cancellous bone. There was no appreciable differences between female and male rats in the distribution and expression levels of ERbeta mRNA in bone. These results indicate that ERbeta mRNA is highly expressed in osteoblasts in rat bone, suggesting that there is a distinct mechanism of estrogen action mediated by ERbeta in bone.