Metabolism of 1-14C linolenic acid in developing brain. II. Incorporation of radioactivity from 1-14C linolenate into brain lipids

Metabolism of 1-14C linolenic acid was studied in growing animals by injecting the tracer intraperitoneally into 12-13 day old suckling rats and following up the results by sacrificing groups of animals at 8 hr, 48 hr, 15 day, and 45 day intervals. In the first 15 days, there was a greater decrease in radioactivity of brain total lipids compared to the later period, although the earlier age period is characterized by lipid deposition rather than breakdown. Results showed that 8 hr after the tracer phosphatidyl choline had the highest specific radioactivity. When the total phosphatidyl ethanolamine fraction was resolved into diacyl and alk-l-enyl species, it was found that radioactivity was not distributed evenly between the two species. There was a progressive increase in radioactivity of the alkenyl and a decrease in the diacyl species. Forty-eight hr after the tracer, however, the radioactivity of phosphatidyl ethanolamine increased and at 45 days remained slightly higher than phosphatidyl choline. Radioactivity of cholesterol, a result of synthesis from acetate undoubtedly derived from the breakdown of tracer linolenate, was also high 48 hr after tracer and remained high until 45 days