Department of Veterinary Physiology, School of Veterinary Medicine, Rakuno Gakuen University, 582-1 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan.
Histochem Cell Biol. 2009 Oct;132(4):447-55. doi: 10.1007/s00418-009-0621-1. Epub 2009 Jul 28.
This study is the first to examine the expression of the 14 monocarboxylate transporter genes (MCT1-MCT14) in the mammary gland of mammals. RT-PCR, Western blot, immunohistochemistry, and immunofluorescence confocal laser microscopy were applied in a comprehensive approach to assess the expression and cellular localization of MCTs in the mammary gland of lactating cattle. RT-PCR revealed the existence of nine MCT isoforms, namely MCT1, MCT2, MCT3, MCT4, MCT5, MCT8, MCT10, MCT13, and MCT14 in cow mammary gland. The amplified cDNA segments were confirmed by sequence analysis and deposited in the GenBank. Using the commercially available antibodies against MCT1-MCT8, Western blotting verified the protein expression of MCT1, MCT2, MCT3, MCT4, MCT5, and MCT8 in the cow mammary gland. The precise cellular localization of the identified MCT proteins showed that both MCT1 and MCT2 were basolaterally localized on the cow mammary alveolar epithelial cells. In contrast, MCT4 protein signal was expressed on the apical membrane of these alveolar epithelia. MCT8, however, was predominantly localized on the basolateral membranes of the lactocytes, along with its weak labeling on the apical membrane of the same cells. No immunoreactive staining for MCT3 and MCT5 proteins could be detected histochemically in lactating bovine mammary tissue. Additionally, we proved the colocalization of CD147 with both MCT1 and MCT4 on the boundaries of the cow mammary alveolar epithelia. The existence and localization pattern of MCT genes in the mammary gland of lactating cows suggest their possible involvement in the transport of essential elements required for milk synthesis and secretion.
这项研究首次检测了哺乳动物乳腺中 14 种单羧酸转运体基因（MCT1-MCT14）的表达。通过 RT-PCR、Western blot、免疫组织化学和免疫荧光共聚焦激光显微镜，综合评估了 MCTs 在泌乳牛乳腺中的表达和细胞定位。RT-PCR 显示，在奶牛乳腺中存在 9 种 MCT 同工型，即 MCT1、MCT2、MCT3、MCT4、MCT5、MCT8、MCT10、MCT13 和 MCT14。通过序列分析确认扩增的 cDNA 片段，并将其存入 GenBank。使用市售的针对 MCT1-MCT8 的抗体，Western blot 验证了 MCT1、MCT2、MCT3、MCT4、MCT5 和 MCT8 在奶牛乳腺中的蛋白表达。鉴定的 MCT 蛋白的精确细胞定位表明，MCT1 和 MCT2 均在奶牛乳腺肺泡上皮细胞的基底外侧定位。相比之下，MCT4 蛋白信号在这些肺泡上皮的顶膜上表达。然而，MCT8 主要定位于泌乳细胞的基底外侧膜上，同时在同一细胞的顶膜上也有较弱的标记。在泌乳牛乳腺组织中，MCT3 和 MCT5 蛋白的免疫组织化学染色未能检测到。此外，我们证明了 CD147 与 MCT1 和 MCT4 在奶牛乳腺肺泡上皮的边界处共定位。泌乳奶牛乳腺中 MCT 基因的存在和定位模式表明它们可能参与了运输合成和分泌乳汁所需的必需元素。
