AJP - Endocrinology and Metabolism, Vol 239, Issue 6 407-E411, Copyright © 1980 by American Physiological Society
In vivo incorporation of tritium from 3H2O into pulmonary lipids of meal-fed and starved rats
D. A. Todhunter and R. W. Scholz
In vivo fatty acid synthesis, as measured by tritium incorporation from
3H2O into fatty acids, was examined in the lungs of meal-fed and starved
rats. In meal-fed animals, 74% of the radioactivity isolated from pulmonary
lipids was found in the phospholipid fraction, with phospholipid fatty
acids accounting for approximately 89% of total radioactivity in this
fraction. Starving rats for 72 h markedly reduced in vivo 3H2O
incorporation into pulmonary lipids. Intraperitoneal injection of
(-)-hydroxycitrate prior to 3H2O administration also markedly reduced
isotope incorporation into pulmonary lipid fractions of fed rats. These
studies demonstrated net in vivo synthesis of fatty acids in pulmonary
tissue of rats using a method that is not complicated by potential
differences in metabolic pool sizes or peculiarities of specific carbon
substrate sources. Synthesis of fatty acids in vivo was affected by the
nutritional state of the animal and citrate appears to be a significant
source of cytoplasmic acetyl-CoA for de novo pulmonary lipogenesis in the
fed rat.
