Temporal variations in microsomal lipid peroxidation and in glutathione concentration of rat liver.

The temporal variation in the NADPH-dependent lipid peroxidation and glutathione-S-transferase activity and in the concentration of cytosolic and microsomal proteins and in reduced glutathione of rat liver were investigated at 0100, 0500, 0900, 1300, 1700, and 2100 in male Sprague-Dawley rats synchronized to a 12-hr light-dark cycle. Highly significant time-dependent variations were obtained in the microsomal rate of lipid peroxidation, and in the concentration of reduced glutathione and cytosolic and microsomal protein. The maximal mean values for the lipid peroxidation, for the concentration of reduced glutathione, and of cytosolic and microsomal proteins were obtained at 1300, 0900, 0100 and 2100, respectively, whereas the corresponding minimal values were determined at 0100, 1700, 0900, and 1700. There was no temporal variation in the glutathione-S-transferase activity of rat liver. The temporal variation in microsomal peroxidation and in the concentration of reduced glutathione exhibited a characteristic circadian rhythm. There was no reverse relationship between the daily variation in the rate of microsomal lipid peroxidation and the hepatic concentration of reduced glutathione.