FATTY ACID UPTAKE BY BRAIN .2. INCORPORATION OF [I-14C] PALMITIC ACID INTO ADULT RAT BRAIN

The incorporation of radioactivity into brain tissue lipids after feeding [1-14C] palmitic acid to adult rats is reported in the present study. It was noted that: 1. 1. Palmitic acid was incorporated into the brain tissue lipids to the extent of 0.02% of the fed dose, which is about the same as observed in the case of [1-14C] acetate in earlier studies. 2. 2. The observed radioactivity in the brain could not have been contributed by trapped blood because of the very low specific activity of the circulating blood. It was also noted that all the brain tissue total lipid components such as lecithin, phosphatidyl ethanolamine, cerebrosides and phosphatidyl serine were labeled indicating uptake of palmitate by the brain tissue. 3. 3. During the entire period of 1-24 h after feeding, the palmitic acid isolated from the brain tissue had 85-87% of the total radioactivity in the carboxyl carbon. This clearly demonstrated that palmitic acid was largely incorporated unchanged into the brain tissue lipids rather than synthesized from acetate derived from its oxidation. 4. 4. A low activity in the brain tissue cholesterol showed that a small amount of the fed palmitic acid must have been degraded to give radioactive acetate. This also resulted in labeling of stearic acid by chain elongation. © 1969.