THE METABOLISM OF [1‐¹⁴C]ARACHIDONIC ACID IN THE NEUTRAL GLYCERIDES AND PHOSPHOGLYCERIDES OF MOUSE BRAIN¹

Abstract— [1‐ 14 C]Arachidonic acid was incorporated into brain lipids with a half‐life of approx. 5 min. Within 40 min after intra‐cerebral injection, radioactivity was distributed mainly among the diacyl‐ sn ‐glycero‐3‐phosphorylcholine (45 per cent), diacyl‐sn‐glycero‐3‐phosphorylinositol (22 per cent), diacyl‐ sn ‐glycero‐3‐phosphorylethanolamine (14 per cent) and triacylglycerols (9 per cent). At comparable times, the proportions of radioactivity distributed in diacyl‐ sn ‐glycero‐3‐phosphorylserines and alkenylacyl‐ sn ‐glycero‐3‐phosphorylethanolamines were relatively small. Radioactivity was initially incorporated into the phosphatidio acids and diacylglycerols before labelling of the triacylglycerols and other phosphogly‐cerides. The relative specific activity of diacylglycerols was maximum between 3–6 min after injection. Due to the small level of diacyl‐ sn ‐3‐phosphorylinositol present in brain, its relative specific radioactivity was higher than other types of brain phosphoglycerides. Results of the experiment thus indicate that labelled arachidonic acid is an excellent precursor for metabolic studies with regard to acyl groups present in the 2‐position of the phosphoglyceride molecules. Furthermore, this labelled precursor is specially useful in studies related to metabolism of diacyl‐ sn ‐glycero‐3‐phosphorylinositol in brain.