Abstract
Artibeus lituratus is an important species of bat of the Phyllostomidae family. Despite its wide distribution, detailed studies on the mammary gland of this species are lacking. Therefore, this study aimed to evaluate the development, lactation, and hormonal regulation of the mammary gland of A. lituratus during different reproductive stages, with an emphasis on estradiol and progesterone signaling. Fifteen sexually mature adult females were collected, divided into three sample groups based on their reproductive status and subjected to anatomical, histological, morphometric, and immunohistochemical analyses. The results revealed that the mammary gland of A. lituratus exhibited a pattern very similar to that of other mammals. However, some notable differences were observed, including an epithelium composed of epithelial, basal, and myoepithelial cells, as well as continuous remodeling, branching, and renewal of the gland during lactation, accompanied by marked epithelial cell death. The branching of the mammary gland during advanced pregnancy appears to be stimulated by elevated serum estradiol levels, which promote ductal proliferation via ERα activation, and by increased progesterone levels, which, through PR activation and in conjunction with prolactin, stimulate side branching and alveolar development.