Effects of exogenous fatty acids and inhibition of de novo fatty acid synthesis on disaturated phosphatidylcholine production by fetal lung cells and adult type II cells.

De novo fatty acid synthesis may be an important source of saturated fatty acids for fetal lung disaturated phosphatidylcholine (DSPC) production. To investigate the roles of de novo fatty acid synthesis and exogenous fatty acids, we incubated dispersed fetal lung cells and freshly isolated adult type II cells with exogenous palmitate and oleate and measured DSPC synthesis. Unlike adult type II cells, fetal lung cells did not increase DSPC synthesis when exogenous palmitate was available; adult type II cells increased DSPC synthesis by 70% in the presence of palmitate. Exogenous oleate decreased DSPC synthesis by 48% in fetal cells but not in adult type II cells. Incubation of fetal lung cells with TOFA [2-furancarboxylate, 5-(tetradecyloxy)-sodium], a metabolic inhibitor of fatty acid synthesis, decreased fatty acid synthesis by 65%. There was a simultaneous 56% inhibition of DSPC production, but no effect on protein, DNA, or glyceride-glycerol production, measured by precursor incorporation. The inhibition of DSPC synthesis associated with TOFA was partially prevented by exogenous palmitate but not oleate. Fetal cells prepared from explants that had been cultured in dexamethasone also had TOFA-associated inhibition of DSPC synthesis that was similar to non-dexamethasone-exposed cells. These studies suggest that under baseline conditions of low fatty acid availability, such as in the fetus, de novo fatty acid synthesis in fetal cells, but not in adult type II cells, provides sufficient saturated fatty acids to support maximal DSPC production. Inhibition of de novo fatty acid synthesis resulting in decreased DSPC production in fetal lung cells in conditions of low fatty acid availability suggests that fatty acid synthesis may be central to maintain DSPC synthesis in the fetus.