Free radicals have been theorized to play a causative role in the normal ag
ing process. To date, methods used to detect oxidative stress in aged exper
imental animals have only detected 2- to 3-fold differences or less between
young and aged animals. Measurement of F-2-isoprostanes has emerged as pro
bably the most reliable approach to assess oxidative stress status in vivo.
Therefore, we measured levels of F-2-isoprostanes free in plasma and level
s esterified in plasma lipids in young rats (3-4 months of age) and aged ra
ts (22-24 months of age). Plasma concentrations of free F-2-isoprostanes we
re increased dramatically by a mean of 20.3-fold (range 4.3 to 42.9-fold) a
nd levels esterified in plasma lipids were also strikingly increased by a m
ean of 29.9-fold (range 15.8 to 50.0-fold). These findings unveil profound
oxidative stress in aged rats which adds considerable support for the free
radical theory of aging. (C) 2001 Academic Press.