The effect of light duration on weight, hormonal parameters and oxidative stress indexes in young white male rats: An experimental study

Objective: Assessing the effects of light exposure at night is crucial because it disrupts melatonin production, a key regulator of circadian rhythms and growth processes. This study aimed to determine how exposure to nighttime lighting affects melatonin and physiological properties in young white male rats. Method: Fifty-two male rats (20–25 days old, 85–100g) were divided into four groups and treated for 15 days under a 12-hour light/dark cycle. The control group (C) had a normal cycle, while groups T1, T2, and T3 were exposed to continuous light for 4, 8, and 12 hours, respectively. Melatonin, MDA, GPX, and SOD levels were measured. Statistical analysis was performed using SPSS v.25 with significance set at P≤0.05. Results: Treated groups showed significantly higher body and brain weights compared to the control, though pituitary and thyroid weights showed no significant differences. Melatonin levels dropped significantly in treated groups, while MDA and GPX levels increased. SOD levels were higher in the control group. Brain weights in treatment groups were (1.21±0.039, 0.95±0.004, 1.1±0.95) vs. control (0.96±0.017); melatonin (168.3±7.881, 114.2±4.133, 62.8±1.212) vs. control (189.2±9.815); MDA (3.04±0.037, 3.9±0.065, 4.99±0.353) vs. control (1.9±0.418); GPX (3.07±0.073, 3.9±0.279, 4.5±0.346) vs. control (2.3±0.233); and SOD (1.76±0.256, 1.54±0.133, 1.06±0.153) vs. control (2.01±0.096). Conclusion: Our findings revealed that exposure to artificial lighting can have adverse effects on our bodies. This includes lowering melatonin levels while increasing body weight and ushering negative impacts on oxidative markers.