Free radical theory of aging: effect of age, sex and dietary precursors on rat-brain docosahexanoic acid.

Increasing the peroxidizability of dietary fat has an adverse effect on the function of the central nervous system (CNS) in the rat. This effect may be influenced by the level of docosahexanoic acid, a highly unsaturated fatty acid, selectively concentrated in the phospholipids of brain membranes. This study was aimed at determining the influence of age, sex, and the nature of a dietary lipid supplement - linolenic acid (18:3w3), docosahexanoic acid (22:6w3), or the same amount of 22:6w3 in the form of menhaden oil triglycerides - on the rate of increase in the percentage of 22:6w3 in the whole-brain fatty acids of rats between the ages of 1 and 12 months. The dietary lipid supplements were reflected in linear increases in the brain 22:6w3 of female rats throughout the study. Between 6 and 12 months of age, the rate of incorporation of dietary 22:6w3 and its precursors into the brain 22:6w3 of male rats dropped. At 12 months it was about half that for females in the case of 22:6w3 and menhaden oil, and about zero for 18:3w3. It is suggested that dietary 22:6w3 and its precursors may modify CNS function by altering membrane function and peroxidizability through changes in the concentration of 22:6w3 in membrane phospholipids.