EFFECT OF AGE AND EXTENT OF DIETARY RESTRICTION ON HEPATIC-MICROSOMALLIPID-PEROXIDATION POTENTIAL IN MICE

Lipid peroxidation potential in hepatic microsomes from young and old mice following two different caloric restriction regimens was measured by a colorimetric thiobarbituric acid method under conditions where F e2+ autoxidation and free oxygen radical production were undetectable. Peroxidation was highest in the young (3.5-month-old) slightly restri cted group (caloric intake 75% of ad libitum mice) but very low in you ng severely restricted (caloric intake 50% of ad libitum mice) and in both old (27-month-old) slightly and severely restricted groups. Very old (45-month-old) severely restricted animals had intermediate lipid peroxidation potentials. Fatty acid composition of liver homogenates w as also determined. Significant differences between groups were found for only three fatty acids.;linoleic acid (18:2(n-6)) decreased in age d slightly restricted animals while it remained stable in severely res tricted animals during aging. Dihomo-gamma-linolenic acid (20:3(n-6)) was higher in very old restricted animals than in old slightly restric ted animals. Docosahexaenoic acid (22:6(n-3)) decreased in old slightl y restricted animals. These results indicated that the effect of diets on hepatic fatty acid composition and the potential for microsomal li pid peroxidation in mice was dependent on the degree of caloric restri ction and age.