# Morphophysiology and Hormonal Control of the Mammary Gland of the Bat Artibeus lituratus During Gestation and Lactation: Emphasis on Estradiol and Progesterone

## TL;DR

This study examines how the mammary gland of the bat Artibeus lituratus develops and functions during pregnancy and lactation, focusing on the roles of estradiol and progesterone.

## Contribution

The study provides new insights into the hormonal regulation of mammary gland development in bats, highlighting unique morphological and physiological features.

## Key findings

- The mammary gland of A. lituratus shows continuous remodeling during lactation, with marked epithelial cell death.
- Elevated estradiol and progesterone levels stimulate ductal proliferation and alveolar development through ERα and PR activation.

## 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.

The mammary gland of NON females of Artibeus lituratus was composed of few ducts interspersed within a rich stroma, and covered by adipose tissue. The branching of the mammary gland in AP females are triggered by stimuli from an increase in serum estradiol that, through ERα activation, stimulates the proliferation of the ducts, and an increase in serum progesterone that, through PR activation, in conjunction with prolactin, stimulates side branching and alveolar formation. (AP, advanced pregnancy; Arrows, mammary tubules; At, adipose tissue; L, lumen; LAC, lactating; NON, non‐reproductive; S, stroma)