Broxuridine

The development and lactation of the mammary gland are critical for the survival and growth of offspring in mammals. In particular, mammary development during puberty plays a pivotal role in establishing the ductal system for lifelong lactation performance. To investigate the role of N-carbamylglutamate (NCG) in regulating mammary gland development during puberty, 5-mo-old ewe lambs (n = 96) were randomly assigned to either control group (basal diet) or an NCG group (basal diet + 2 g/d NCG) for 59 d. At the end of the trial, serum and mammary gland samples were collected for hormone assays, histological staining, bromodeoxyuridine (BrdU)-based cell proliferation analysis, and transcriptome profiling. Randomly selected animals (n = 5 per group) from both groups received 3 intravenous injections of BrdU before mammary tissue collection. The NCG supplementation was found to increase serum estrogen (E2, P = 0.036) and IGF-1 (P = 0.035) and plasma arginine concentrations by 31.4% (P < 0.001) compared with control groups. Histological analysis revealed enhanced ductal development (P < 0.001) and a higher proportion of BrdU-positive epithelial cells (P = 0.004) in NCG versus control ewes, suggesting stimulated epithelial proliferation. Transcriptomic analysis of mammary tissue (n = 5 per group) identified 254 differentially expressed genes (182 upregulated, 72 downregulated) in the NCG group, which were enriched in biological processes related to epidermal development, branching morphogenesis, and hormone-related pathways, including hormone metabolic process, estrogen receptor (ER) pathway, and IGF-1 receptor (IGF-1R) signaling. Notably, NCG increased the ratio of ER- (P = 0.026) and progesterone receptor-positive epithelial cells compared with the control groups, along with significantly upregulated gene responses to ER, IGF-1R activity, and cell proliferation. These findings highlight a role of NCG in promoting pubertal mammary gland development by increasing systemic E2 and IGF-1 levels and promoting hormone-responsive gene expression, ductal morphogenesis, and epithelial cell proliferation.