Fatty acid metabolism in human fetal placental vasculature

The utilization of exogenous acetate and palmitate for the synthesis of vascular wall lipids was studied in isolated blood vessels of the human placenta under high- and low-oxygen conditions. Arteries and veins were obtained from fresh placental material and incubated in Krebs-Henseleit buffer (pH 7.4 at 37 degrees C) containing (in mM) either [2-14C]acetate, 0.11; [1-14C]palmitate, 0.43; or [16-14C]palmitate, 0.43. At the end of the 180-min incubation, neutral lipids accounted for 40%, and phospholipids 60%, of the 14C recovered. Following incubation with either precursor, 14C label was recovered mainly in 16-carbon fatty acids (FA) (35%) and 18-carbon FA (45%); less than 10% was recovered in less than or equal to 14-carbon FA and greater than or equal to 20-carbon FA. Estimates of synthesis rate however indicated that the 18- and 20-carbon FA had the highest turnover rates. Schmidt degradation analysis demonstrated considerable labeling of alkyl carbons after incubation with either carboxyl- or alkyl-labeled precursors, indicating that FA degradation products were used for de novo FA synthesis. Collectively, these findings suggest the presence of both de novo and chain elongation pathways. No differences were observed between arteries and veins, and anoxia had little influence on FA metabolism. Analysis of ATP levels demonstrated elevated concentrations of ATP present, accounting for the apparent lack of anoxic inhibition of FA metabolism.