Matsumura Ryusei, Takagi Chika, Kakeya Tomoshi, Okuda Kiyoshi, Takeuchi Sakae, Takahashi Sumio
Department of Biology, Faculty of Science, Faculty of Agriculture, Okayama University, Okayama, Japan.
Neuroendocrinology. 2003 Aug;78(2):96-104. doi: 10.1159/000071965.
The intermediate lobe of rodent pituitaries is involved in the regulation of prolactin (PRL) secretion from the anterior lobe. In a previous study, we demonstrated the stimulatory effect of alpha-melanocyte-stimulating hormone (alpha-MSH) on PRL release and the expression of melanocortin-3 receptors (MC3-Rs) in cultured mouse pituitary cells. The aim of the present study was to clarify whether alpha-MSH directly stimulates PRL release through the MC3-Rs by determining the cell type of MC3-R-expressing cells in the mouse pituitary anterior lobe. Northern blot analysis revealed a 2.7-kb transcript for MC3-R mRNA in the anterior and neurointermediate lobes of pituitary glands of adult male and female mice. Dual cellular localization of MC3-R mRNA and PRL or growth hormone (GH) in the mouse pituitary glands was performed by in situ hybridization analysis of MC3-R mRNA followed by immunocytochemical detection of PRL or GH. MC3-R mRNA was detected in most mammotropes and some somatotropes. alpha-MSH increased PRL release and stimulated DNA replication in mammotropes, and these effects were blocked by SHU9119, an antagonist of MC3-R and MC4-R. These results indicate that alpha-MSH stimulates PRL release and proliferation of mammotropes through MC3-Rs, and suggest that alpha-MSH from intermediate lobes can regulate mammotrope functions in the mouse pituitary.
啮齿动物垂体的中间叶参与调节前叶催乳素（PRL）的分泌。在先前的一项研究中，我们证明了α-黑素细胞刺激素（α-MSH）对培养的小鼠垂体细胞中PRL释放和黑皮质素-3受体（MC3-Rs）表达的刺激作用。本研究的目的是通过确定小鼠垂体前叶中表达MC3-R的细胞类型，来阐明α-MSH是否通过MC3-R直接刺激PRL释放。Northern印迹分析显示，成年雄性和雌性小鼠垂体前叶和神经中间叶中存在一条2.7 kb的MC3-R mRNA转录本。通过对MC3-R mRNA进行原位杂交分析，随后对PRL或生长激素（GH）进行免疫细胞化学检测，对小鼠垂体中MC3-R mRNA与PRL或GH进行双重细胞定位。在大多数催乳素细胞和一些生长激素细胞中检测到MC3-R mRNA。α-MSH增加了催乳素细胞中PRL的释放并刺激了DNA复制，而这些作用被MC3-R和MC4-R的拮抗剂SHU9119阻断。这些结果表明，α-MSH通过MC3-R刺激催乳素细胞释放PRL和增殖，并提示中间叶的α-MSH可以调节小鼠垂体中催乳素细胞的功能。
