RESUMO
<p><b>OBJECTIVE</b>To investigate the expressions of the stem cell antigen-1 (Sca-1), Mucin1 (Muc1) and CD24 in quiescent mammary glands of female rats.</p><p><b>METHODS</b>The expressions of CD24 and Sca-1 were detected in 6- and 9-week-old female rat mammary gland by Western blotting. Sections (4 microm) of 6- and 9-week-old female SD rat mammary gland were prepared to observe the expressions of Sca-1, Muc1 and CD24 by immunohistochemical labeling and immunofluorescence labeling.</p><p><b>RESULTS</b>CD24 and Sca-1 in the mammary glands were expressed at lower level in 6-week-old female rats than in 9-week-old female rats. Sca-1 expression was detected in the mammary gland ductus, branching ductus, and areas surrounding the gland alveolus; CD24 was expressed in the mammary gland branching ductus and fat pads, and also the regions surrounding the gland alveolus. Muc1 expression was localized in the mammary gland ductus and branching ductus.</p><p><b>CONCLUSIONS</b>Sca-1-, CD24- and Muc1-positive cells may represent mammary gland progenitor cells, mammary gland stem cells, and mammary gland mature epithelium cells, respectively. This study provides some morphological evidences for identifying these cells, but they still need further verifications in cellular transplantation experiments.</p>