11,12-Epoxyeicosatrienoic acid (CAS: 81276-02-0) is an epoxyeicosatrienoic acid (EET). Induction of CYP2C8 in native coronary artery endothelial cells by beta-naphthoflavone enhances the formation of 11,12-epoxyeicosatrienoic acid, as well as endothelium-derived hyperpolarizing factor-mediated hyperpolarization and relaxation. Transfection of coronary arteries with CYP2C8 antisense oligonucleotides resulted in decreased levels of CYP2C and attenuated the endothelium-derived hyperpolarizing factor-mediated vascular responses. Thus, a CYP-epoxygenase product is an essential component of the endothelium-derived hyperpolarizing factor-mediated relaxation in the porcine coronary artery, and CYP2C8 fulfills the criteria for the coronary endothelium-derived hyperpolarization factor synthase. The role of EETs in the regulation of the cerebral circulation has become more important since it was realized that EETs are produced in another specialized cell type of the brain, the astrocytes. It has become evident that EETs released from astrocytes may mediate cerebral functional hyperemia. Molecular and pharmacological evidence has shown that neurotransmitter release and spillover onto astrocytes can generate EETs. Since these EETs may reach the vasculature via astrocyte foot-processes, they have the same potential as their endothelial counterparts to hyperpolarize and dilate cerebral vessels. P450 enzymes contain heme in their catalytic domain and nitric oxide (NO) appears to bind to these heme moieties and block formation of P450 products, including EETs. Thus, there appears to be crosstalk between P450 enzymes and NO/NO synthase. The role of fatty acid metabolites and cerebral blood flow becomes even more complex in light of data demonstrating that cyclooxygenase products can act as substrates for P450 enzymes (PMID: 17494091, 17434916, 17406062, 17361113, 15581597, 11413051, 10519554). EETs function as autocrine and paracrine mediators. During inflammation, a large amount of arachidonic acid (AA) is released into the cellular milieu and cyclooxygenase enzymes convert this AA to prostaglandins that in turn sensitize pain pathways. However, AA is also converted into natural EETs by cytochrome P450 enzymes. Cytochrome P450 (CYP) epoxygenases convert arachidonic acid into four epoxyeicosatrienoic acid (EET) regioisomers, 5,6-, 8,9-, 11,12-, and 14,15-EET. EETs produce vascular relaxation by activating smooth muscle large-conductance Ca2+-activated K+ channels. In particular, 11,12-epoxy-5Z,8Z,14Z-eicosatrienoic acid has been shown to play a role in the recovery of depleted Ca2+ pools in cultured smooth muscle cells (PMID: 9368016). In addition, EETs have anti-inflammatory effects on blood vessels and in the kidney, promote angiogenesis, and protect ischemic myocardium and the brain. EET levels are typically regulated by soluble epoxide hydrolase (sEH), the major enzyme degrading EETs. Specifically, soluble epoxide hydrolase (sEH) converts EETs into dihydroxyeicosatrienoic acids.