DOES AN INCREASE IN DIETARY LINOLEIC-ACID MODIFY TISSUE CONCENTRATIONS OF CERVONIC ACID AND CONSEQUENTLY ALTER ALPHA-LINOLENIC REQUIREMENTS- MINIMAL REQUIREMENT OF LINOLEIC-ACID IN ADULT-RATS

Rats were fed a control diet containing both linoleic and alpha-linole nic acid. When 60-days-old they were divided into 8 groups, each recei ving the same amount of alpha-linolenic acid, but varying amounts of l inoleic acid. When the (n-6)/(n-3) ratio in the diet varied from 2 to 32 (with a constant amount of 150 mg alpha-linolenic acid per 100 g di et), tissue levels of the (n-3) series fatty acids were not significan tly modified, except in the liver, heart and testes. In all organs stu died, the saturated and monounsaturated fatty acids were practically u nchanged. For the (n-6) series fatty acids, arachidonic acid was not s ignificantly affected, in muscle, kidney, brain, myelin, nerve-endings or sciatic nerve, whatever the quantity of linoleic acid in the diet. In liver, arachidonic acid plateaued at 2400 mg linoleic acid/ 100 g diet and at 400 mg /100g diet in heart. Results for 22:5(n-6) showed a marked increase in heart, a moderate increase in liver and kidney, an d no effect in muscle, testes, brain, myelin, nerve-endings or sciatic nerve. This experiment defined the minimum amount of linoleic acid re quired in the diet to maintain fatty acids of the linoleic family in t he young adult rat. For the first time it was demonstrated that 1200 m g/100 g diet are sufficient for the liver, as evidenced by maintenance of the arachidonic acid concentration. For the other organs, there is either a very marked preservation of this acid, or the dietary level is less than 300 mg/100 g diet. For the essential fatty acid precursor s (i.e. linoleic and alpha-linolenic acids), the optimal (n-6)/(n-3) r atio required in the diet is about 8.