Oleic acid-C is intended for use as an internal standard for the quantification of oleic acid by GC- or LC-MS. Oleic acid is a monounsaturated fatty acid and a major component of membrane phospholipids that has been found in human plasma, cell membranes, and adipose tissue. It contributes approximately 17% of the total fatty acids esterified to phosphatidylcholine, the major phospholipid class in porcine platelets. Oleic acid inhibits collagen-stimulated platelet aggregation by approximately 90% when used at a concentration of 10 µg/ml. It also inhibits fMLF-induced neutrophil aggregation and degranulation by 55 and 68%, respectively, when used at a concentration of 5 µM, similar to arachidonic acid Oleic acid (60 µM) induces release of intracellular calcium in human platelets. In vivo, oleic acid increases TNF-α, IL-8, IL-6, and IL-1β production, neutrophil accumulation, and apoptotic and necrotic cell death in mouse lung and has been used to induce lung injury in a mouse model of acute respiratory distress syndrome (ARDS).