Background

Linoleic acid is the predominant polyunsaturated fatty acid (PUFA) in the human diet. The hydroxyoctadecadienoic acid (HODE) derivatives of linoleic acid, 9(S)-HODE, 9(R) HODE, and 13(S)-HODE, are the most widely distributed of the known linoleic acid metabolites. HODEs can be generated enzymatically by cyclooxygenase, lipoxygenase, and some cytochrome P450s. However, the bulk of linoleic acid peroxidation, especially generation of 9-HODEs, occurs by non-enzymatic processes so that HODEs are excellent indicators of free radical mediated lipid peroxidation. In mammalian cells, free radicals are derived primarily from peroxide and singlet oxygen, which are referred to as reactive oxygen species (ROS). ROS-derived free radicals include the super-oxide anion and the hydroxyl radical. Most ROS diffuse only a nanometer or so before reacting. Among the most important targets of free radical reactions in vivo are lipids, and resultant oxidized lipids can travel throughout the circulatory system.

Assay Principle

This kit is a competitive enzyme-linked immunoassay (ELISA). Briefly, the 9-HODE present in the samples or standards competes with 9(±)-HODE conjugated to horseradish peroxidase [9(±)-HODE-HRP] for binding to an
antibody specific for 9(±)-HODE that is precoated on a microplate. The peroxidase activity of 9(±)-HODE-HRP results in color development when a substrate is added. The intensity of the color is proportional to the amount of 9(±)-HODE-HRP bound and is inversely proportional to the amount of unconjugated 9-HODE present in the samples or standards.