AJP - Endocrinology and Metabolism, Vol 240, Issue 4 435-E440, Copyright © 1981 by American Physiological Society
Reutilization of fatty acid carbons for lung lipid synthesis
J. L. Rabinowitz, T. Cardwell and D. J. Bassett
The utilization of glucose, palmitate, and oleate for the synthesis of lung
lipids was studied in isolated rat lungs. Lungs were ventilated with 5% CO2
in air and perfused for 100 min with a Krebs-Ringer bicarbonate buffer (pH
7.4), containing 3% fatty acid-free albumin and either 5.6 mM
[U-14C]glucose or 0.25 mM [1-14C]palmitate, or 0.25 mM [1-14C]-oleate. At
the end of 100 min of perfusion with these precursors, between 73 and 85%
of total lipid 14C was recovered as phospholipid. Glucose carbon was mainly
incorporated into triglyceride fatty acids (TG-FA) and phosphatidylcholine
fatty acids (PC-FA) of 16- and 18-carbon chain length. After perfusion with
[14C]palmitate and [14C]oleate, only 65 and 20% of 14C was recovered as PC
16-carbon and 18-carbon FA, respectively. The remaining 14C was mainly
recovered as FA shorter than the 14C precursors. Schmidt degradation
analysis of lipid FA demonstrated considerable labeling of alkyl carbons on
perfusion with the carboxyl-labeled precursors, indicating that FA
degradation products were used for synthesis of lipid FA. This process was
enhanced on addition of glucose to the perfusate.
