COMPARISON OF RECOVERY OF PREVIOUSLY DEPRESSED HEPATIC DELTA-6 DESATURASE ACTIVITY IN ADULT AND OLD RATS

The ability to recover hepatic Delta 6 desaturase (Delta 6D) activity with linoleic acid as substrate was compared in adult and old rats. Male rats fed a diet deficient in alpha-linolenic acid were used either at 6 or 21 months. From these two ages onward, animals were fed a diet containing 10% fish oil for 3 months to reduce Delta 6D activity. After this period, some of the animals were killed. The other animals were returned to the original diet deficient in alpha-linolenic acid. Fatty acid composition in liver and brain and hepatic Delta 6D activity were analysed 3 and 7 days after the change in diet. When rats were fed the diet containing 10% fish oil, Delta 6D activity was lower than in those fed the diet deficient in alpha-linolenic acid. The liver fatty acid composition was altered with disappearance of 22:5 n-6 and a decrease in 18:2 n-6, 20:4 n-6 and 22:4 n-6 accompanied by an increase in 20:5 n-3, 22:5 n-3 and 22:6 n-3. When rats were re-fed the original diet, Delta 6D activity returned after 3 days to its initial level in the 9-month-old rats; in 24-month-old animals, recuperation was incomplete. The levels of 20:4 n-6 and 18:2 n-6 increased in the liver concurrently with a decrease in levels of 20:5 n-3, 22:5 n-3 and 22:6 n-3. In both age groups, the brain fatty acid profile remained unchanged 7 days after returning to the diet deficient in alpha-linolenic acid.