Effect of continuous illumination on the ultrastructure of rat hepatocytes during ontogenesis

Chronic light exposure is a known factor accelerating mammalian aging, primarily through circadian rhythm disruption, oxidative stress, and inflammation. The liver, a central organ in systemic aging, undergoes structural and functional decline with age, including mitochondrial dysfunction, lipid accumulation, and impaired detoxification. This study investigates the impact of constant light exposure on the ultrastructural changes in hepatocytes of Wistar rats across different ontogenetic stages. Male Wistar rats were divided into control (natural light cycle) and experimental (constant light) groups. Liver samples were collected at 6, 12, 18, and 24 months, processed for electron microscopy, and analyzed for hepatocyte morphology, mitochondrial integrity, and Golgi apparatus structure using stereometric methods. Constant light exposure induced premature hepatocyte aging, marked by mitochondrial dysfunction, lipid accumulation, and impaired organelle turnover. These changes suggest accelerated oxidative damage and metabolic dysregulation, likely due to melatonin suppression and circadian disruption. The findings highlight the role of environmental light pollution in promoting liver aging and underscore the need for chronobiological interventions to mitigate age-related hepatic decline. Keywords: Aging, hepatocytes, constant light exposure, mitochondria, ultrastructure