12- and 15-lipoxygenases in rat pineal gland.

A whole organ or a homogenate of rat pineal gland was incubated with arachidonic Acid. Two predominant metabolites were identified by mass spectrometry to be 12-hydroxy-5,8,10,14-eicosatetraenoic acid and 10-hydroxy-11,12-epoxy-5,8,14-eicosatrienoic acid. 15-Hydroxy-5,8,11,13-eicosatetraenoic acid was also formed in a smaller amount. In addition, peroxy acids appeared rapidly only at the initial stage of reaction. In various parts of rat brain the 12-lipoxygenase activity was by far the highest in pineal gland, and less than 5% of the activity was found in pituitary gland and hypothalamus.