RESUMO
E-cadherin [E-cad] is a cell adhesion molecule, essential for the maintenance of the epithelial phenotype. The current study aimed at showing the histological changes and the pattern of E-cad expression in the female rat mammary gland during different stages of their fertile period microscopically and morphometrically. Thirty-five adult female albino rats [3-4 months old] were divided into seven groups [five rats each]: the rats in group I were not pregnant [resting] and groups II-VII were sacrificed at days 7 and 14 of each of their pregnancy, lactation, and weaning stages. The excised right inguinal mammary glands were processed for H and E and E-cad immunostaining. The sections were evaluated microscopically and morphometrically. The mammary gland of nonpregnant rats had abundant adipose connective tissue with few glandular elements. During pregnancy, there was a progressive increase in the alveoli, which became distended with milk, with prominent sac formation during lactation. The E-cad expression pattern was mainly observed as a strong positive linear membranous pattern in all borders of epithelial cell lining, whereas the myoepithelial cells were negative. These observations were found in different groups, except that of lactation, where the pattern was limited to the basolateral membranes of these epithelial cells. Morphometrically, the positive membranous epithelial cells for E-cad, its density area fraction and cytoplasmic positive reaction ranged from 7-83%, 3.9-6.8% and 0-7%, respectively in all groups. In late pregnancy, there was a marked increase in the negative epithelial cells [93%], with a significant decrease in density area fraction expression [3.9%], which was persistent during lactation. Positive E-cad expression of stromal cells was only observed during weaning. The E-cad was mainly localized to the membranes of epithelial cell lining and absent in myoepithelial cells. The quantitative E-cad expression can represent a tool that ensures qualitative microscopic observations during the fertile period