Binding and solubility of oleic acid to laboratory materials: a possible artifact

The possibility that significant amounts of fatty acids were dissolved in or bound to the surfaces of common laboratory materials was examined. The uptake or adsorption of radioisotopically labeled oleic acid and cholic acid by plastic tubing of Tygon, Teflon, and polyethylene, and Pyrex, and borosilicate glass, and steel was measured. 3H-oleic acid and 14C-cholic acid were used in the presence of different concentrations of unlabeled oleic acid, cholic acid, and/or bovine serum albumin. Concentrations, composition, pH, and perfusion rates were varied. Relatively large amounts (10-95%) of oleic acid (25 microM) were lost by dissolving in plastic and adsorption to glass or metal. The degree of losses decreased in the presence of compounds in the perfusion solution which could bind or dissolve oleic acid. In contrast, cholic acid was not lost to plastic, glass or metal. The magnitude of and influence of perfusion rate, composition, pH, and sequence of perfusion solutions on oleic acid losses were sufficiently large that the results of certain studies, such as those of unstirred water layers of albumin - stimulated fatty acid uptake by hepatocytes may need to be reexamined.