Circadian rhythmicity of whole-blood glutathione in healthy subjects

Objectives: Physiologic rhythms of antioxidants have been the subject of considerable interest in recent years. Physiologically, it is known that 24-h variability in whole-blood glutathione (GSH) could depend on various factors, such as meal composition, protein dietary content, meal-related hormonal modifications, and stress. Experiments were conducted to determine if the circadian variations previously observed in hepatic concentrations of reduced glutathione in animals also occurred in healthy volunteers. Methods: The circadian periodicity of whole-blood glutathione was explored. All parameters were measured enzymatically at 4-h intervals over a 24-h period. Results: Circadian rhythms were not found. The rhythms peak for glutathione content occurred at 9 h with a small peak at 21 h. The nadir occurred at 17 h and 1 h. Conclusion: These data show that despite this wide distribution of glutathione throughout the day we could not find any significant intertime variability.