Relative incorporation of linoleic and arachidonic acid in phospholipids and triglycerides of different rat tissues.

Fat-deficient rats were fed different amounts of methyl linoleate for increasing periods of time. The fatty acid composition of triglycerides and phospholipids of epididymal fat pad, epirenal fat depot, intestinal fat depot, liver, and the pool of heart, kidney, lungs and pancreas was determined. The distribution of the total amount of linoleic and arachidonic acid incorporated into phospholipids and triglycerides per rat was calculated. Phospholipids and triglycerides of depot tissues presented different fatty acid compositions.Although the phospholipids of liver and the pool of heart, kidney, lung and pancreas specifically incorporated linoleic acid at the beginning they very rapidly attained a rather steady composition, whereas triglycerides went on incorporating the acid. The amount of linoleic acid incorporated into the phospholipids of depot tissues was rather small. The triglycerides undoubtedly contributed in the highest proportion to the total pool of linoleic acid. However, the highest proportion of arachidonic acid was found in the total pool of phospholipids.The total amount of linoleic acid incorporated into the phospholipids was an approximately lineal function of the amount of phospholipids independent of period of administration and doses of methyl linoleate. Besides presenting two lineal functions of the amount of phospholipids, arachidonic acid showed a vertical increase coincident with a vertical decrease of the amount of eicosa-5,8,11-trienoic acid. At this period no change in the amount of the phospholipid was shown. This phenomenon is explaioned as a possible direct replacement of eicosatrienoic acid by arachidonic acid.