PRODUCTION OF UNESTERIFIED FATTY ACID IN BRAIN

1. 1. Unesterified fatty acids have been isolated by thin-layer chromatography from fresh mouse brain, mouse brain frozen in situ in liquid N2, and slices of whole mouse brain incubated at 37° and 0°, respectively. Higher yields, and different distributions of molecular species, were obtained from frozen brain and incubated slices than were obtained from fresh brain. 2. 2. The combined yield of unesterified fatty acid from subcellular fractions of rat brain was greater than that from unfractionated tissue. Yields from fractions of incubated slices of whole rat brain were greater than those from corresponding fractions isolated from fresh tissue. 3. 3. Different subcellular fractions of rat brain contained different distributions of molecular species. The supernatant fraction was characterised by a low or zero content of arachidonate. [I-14C]Acetate was incorporated into unesterified fatty acid of all isolated fractions of incubated slices. 4. 4. Rat brain mitochondria when subjected to ultrasonic vibration liberated soluble unesterified fatty acid. This was characterised by an absence of arachidonate and a high proportion of monounsaturated acid. 5. 5. Seven unusual components were present in rat brain. After treatment with diazomethane these had the gas-chromatographic properties expected for methyl esters of tridecamonoenoic, pentadecamonoenoic, heptadecamonoenoic, nonadecamonoenoic, tetradecamonoenoic, hexadecatrienoic, and heptadecatrienoic acids. The last three components were detected in mouse brain. © 1968.