Fatty acid and oxylipin concentration differ markedly between different fetal bovine serums: A cautionary note.

Fetal bovine serum (FBS) has been used as a universal supplement in cell culture for more than six decades. This includes the investigation of lipid and lipid mediator formation and biology. Little is known about the (polyunsaturated) fatty acid composition and their oxidation products in FBS. Therefore, we analyzed six different FBS purchased from three different companies regarding their fatty acid and oxylipin concentrations. We found pronounced differences in the fatty acid concentrations. Even two batches of "standardized" FBS batches from one company showed drastic differences (e.g., for eicosapentaenoic acid 5 ± 1 μM vs. 11 ± 1 μM). Oxylipin concentrations also markedly differ between the FBS lots. The highest differences were found for 12-lipoxygenase products (e.g., 12-hydroxyeicosatetraenoic acid free 21-87 nM and total 58-108 nM), probably due to inconsistent serum generation procedures. Our results indicate that for cell culture studies dealing with lipid metabolism, researchers should carefully characterize their used FBS to ensure reliability and reproducibility of study outcomes.