5,6-Epoxyeicosatrienoic acid-d 11 (5,6-EET-d 11 ) is deuterium labeled 5,6-Epoxyeicosatrienoic acid. 5,6-Epoxyeicosatrienoic acid (5,6-EET; (±)5,6-EpETrE) is a fully racemic version of the enantiomeric forms biosynthesized from arachidonic acid by cytochrome P450 enzymes. In solution, 5,6-Epoxyeicosatrienoic acid degrades into 5,6-DiHET and 5,6-δ-lactone, which can be converted to 5,6-DiHET and quantified by GC-MS. In neuroendocrine cells, such as the anterior pituitary and pancreatic islets, 5,6-Epoxyeicosatrienoic acid has been implicated in the mobilization of calcium and hormone secretion. 5,6-Epoxyeicosatrienoic acid is an inhibitor of T-type voltage-gated calcium channels (Cav3) that inhibits isoforms Cav3.1, Cav3.2 ( IC 50 =0.54 μM), and Cav3. and decreases nifedipine-resistant phenylephrine-induced vasoconstriction in isolated mouse mesenteric arteries via Cav3.2 blockade when used at a concentration of 3 μM. In addition, it is a substrate of COX-1 and COX-2 , as measured by oxygen consumption and product formation assays when used at a concentration of 50 μM. (±)5,6-Epoxyeicosatrienoic acid is provided as a mixture of the free acid and lactone.