Snedeker S M, Brown C F, DiAugustine R P
Laboratory of Biochemical Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
Proc Natl Acad Sci U S A. 1991 Jan 1;88(1):276-80. doi: 10.1073/pnas.88.1.276.
Primer-directed enzyme amplification was used to examine epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) mRNA transcripts in mammary glands of young virgin, mature virgin, midpregnant, and midlactating mice. Transcripts for both EGF and TGF-alpha mRNA were detected in virgin and pregnant mice, whereas transcripts for EGF mRNA but not TGF-alpha mRNA were expressed in 10-day lactating mice. TGF-alpha was localized in the epithelial cap-cell layer of the advancing terminal end bud and in the stromal fibroblasts at the base of the terminal end bud; EGF was localized in the inner layers of the terminal end bud and in ductal cells of mammary epithelium. Implantation of pellets containing EGF or TGF-alpha into the regressed mammary gland of ovariectomized mice stimulated the reappearance of end buds; contralateral glands implanted with pellets containing albumin or insulin were not affected. These results indicate that an EGF-receptor-mediated pathway remained intact in the mammary gland epithelium in the absence of ovarian steroids and that local availability of either EGF or TGF-alpha is sufficient to stimulate the pattern of normal ductal growth. The detection of EGF and TFF-alpha transcripts at different stages of mammary gland development and the different patterns of immunolocalization suggest that each polypeptide plays a different role in normal mammary gland morphogenesis.
采用引物定向酶扩增法检测幼年处女、成年处女、妊娠中期和泌乳中期小鼠乳腺中的表皮生长因子（EGF）和转化生长因子α（TGF-α）mRNA转录本。在处女和妊娠小鼠中均检测到EGF和TGF-α mRNA的转录本，而在泌乳10天的小鼠中仅表达EGF mRNA的转录本，未检测到TGF-α mRNA的转录本。TGF-α定位于生长中的终末芽的上皮帽细胞层和终末芽基部的基质成纤维细胞中；EGF定位于终末芽的内层和乳腺上皮的导管细胞中。将含有EGF或TGF-α的小球植入去卵巢小鼠退化的乳腺中，可刺激终末芽重新出现；而植入含有白蛋白或胰岛素小球的对侧乳腺则未受影响。这些结果表明，在缺乏卵巢类固醇的情况下，EGF受体介导的途径在乳腺上皮中保持完整，并且EGF或TGF-α的局部可用性足以刺激正常导管生长模式。在乳腺发育的不同阶段检测到EGF和TGF-α转录本以及不同的免疫定位模式，表明每种多肽在正常乳腺形态发生中发挥不同的作用。
