Utilization of plasma fatty acid in rat brain: distribution of [14C]palmitate between oxidative and synthetic pathways.
Radioactivity within individual brain compartments was determined from 5 min to 44 h after intravenous injection of [14C]palmitate into awake Fischer-344 rats, aged 21 days or 3 months. Total radioactivity peaked broadly between 15 min and 1 h after injection, declined rapidly between 1 and 2 h, and then more slowly. In 3-month-old rats, the lipid and protein brain fractions were maximally labeled within 15 min after [14C]palmitate injection, then retained approximately constant label for up to 2 days. Radioactivity in the aqueous brain fraction comprised mainly radioactive glutamate and glutamine, and peaked at 45 min, when it comprised 48% of total brain radioactivity, then decreased to 27% of the total at 4 h, 15% at 20 h, and 10% at 44 h. Percent distribution of radioactivity within the different brain compartments, 4 h after intravenous injection of [14C]palmitate, was similar in 21-day-old and 3-month-old rats, despite higher net brain uptake in the younger animals. The results indicate that about 50% of plasma [14C]palmitate that enters the brain of adult rats is incorporated rapidly into stable protein and lipid compartments. The remaining [14C]palmitate enters the aqueous fraction after beta-oxidation, and is slowly lost. At 4 h after injection, 73% of brain radioactivity is within the stable brain compartments; this fraction increases to 86% by 20 h.
D000375:Aging / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D005973:Glutamine / Q000378:metabolism; D007700:Kinetics; D050356:Lipid Metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D014018:Tissue Distribution
D000596:Amino Acids; D005732:Gangliosides; D005971:Glutamates; D009419:Nerve Tissue Proteins; D010169:Palmitic Acids; D010743:Phospholipids; D005973:Glutamine; D019308:Palmitic Acid; D018698:Glutamic Acid