EFFECT OF HIGH-FAT CORN-OIL, OLIVE OIL AND FISH OIL ON PHOSPHOLIPID FATTY-ACID COMPOSITION IN MALE F344 RATS

Epidemiological and laboratory animal model studies have provided evid ence that the effect of dietary fat on colon tumorigenesis depends on the amount of fat and its composition. Because of the importance of th e composition of dietary fat and of tissue membrane fatty acid composi tion in tumor promotion, experiments were designed to investigate the relative effects of high fat diets rich in omega3, omega6 and omega9 f atty acids and colon carcinogen on the phospholipid fatty acid composi tion of liver, colon, small intestine, erythrocytes and blood plasma. At 6 wk of age, groups of animals were fed diets containing 5% corn oi l (LFCO), 23.5% corn oil (HFCO), 23.5% olive oil (HFOO), and 20.5% fis h oil plus 3% corn oil (HFFO). Two weeks later all the animals except the vehicle-treated animals received azoxymethane s.c. once weekly for 2 wk at a dose rate of 15 mg/kg body weight. Animals were sacrificed 5 d later and liver, colon, small intestine and erythrocytes and blood plasma were analyzed for phospholipid fatty acids. The results indica te that the phospholipid fatty acid composition of liver, colon and sm all intestine of HFCO diet fed animals, were not significantly differe nt from those fed the LFCO diet. The levels of palmitoleic acid and li noleic acid were increased in erythrocytes and blood plasma of the ani mals fed the HFCO diet compared to those fed the LFCO diet. Feeding th e HFOO diet significantly increased the oleic acid content and decreas ed the linoleic acid and arachidonic acid levels in various organs whe n compared to the HFCO diet. Animals fed the HFFO diet showed a marked increase in eicosapentaenoic acid and docosahexaenoic acid and a decr ease in linoleic acid and arachidonic acid levels as compared to those fed the HFCO diet. The results also indicate that carcinogen treatmen t had only a minimal effect on the phospholipid fatty acid composition .