Glutathione levels in human platelets display a circadian rhythm in vitro

Glutathione (GSH) levels were measured in platelet-rich plasma (PRP) and concentrates at 4 hour intervals during storage. The values fell steadily during the first several hours after collection at 9:00 a.m., reaching the lowest level at midnight, 14 hours later. Subsequently, the levels rose to a new peak value at 4:00 a.m. GSH levels continued to show cyclic variation over the 48 hours examined in this study. Change in schedules of light and dark under which the platelets were stored had no effect on GSH periodicity. Platelets from night shift workers also displayed a similar periodicity to that of day workers. Erythrocytes failed to demonstrate a similar time related variation in GSH levels during storage.