Prolactin Regulates Seasonal Changes in Renal Rheostasis in Djungarian Hamsters.

Seasonal changes in photoperiod regulate multiple physiological systems in vertebrates, including metabolism, reproduction, and immune function. Kidney mass and renal physiology are known to vary annually, but the endocrine and molecular mechanisms underlying these changes are poorly defined. Prolactin (PRL), a photosensitive hormone is implicated in seasonal energy rheostasis, yet its role in programmed regulation of renal physiology is unknown. Using Djungarian hamsters (Phodopus sungorus), we investigated how photoperiod and PRL regulate seasonal changes in kidney mass, morphology, and transcriptome. Ingestive behaviour, kidney histology, and transcriptomic profiles were assessed. We found that long photoperiods and PRL treatment induced renal hypertrophy and convoluted tubule (CT) expansion, whereas exposure to short photoperiods resulted in a reduction in all measurements. Transcriptomic analysis revealed photoperiod- and PRL-responsive gene modules related to mitochondrial metabolism, solute transport, and epithelial remodeling. Among these, Cdh2, encoding N-cadherin, was downregulated by long photoperiods and PRL, and negatively correlated with CT diameter, suggesting a role in epithelial adhesion during tubular expansion. These findings place prolactin as a key hormonal effector for programmed seasonal kidney function and identify Cdh2 as a target to drive renal physiology.