Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 280, Issue 6, Pages H2430-H2440Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.2001.280.6.H2430
Keywords
cytochrome P-450 epoxygenases; n-3 and n-6 polyunsaturated fatty acids; coronary microcirculation
Funding
- NHLBI NIH HHS [P01-HL-49264, HL-63754-01, R01-HL-56670-02] Funding Source: Medline
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Epoxyeicosatrienoic acids (EETs) are released from endothelial cells and potently dilate small arteries by hyperpolarizing vascular myocytes. In the present study, we investigated the structural specificity of EETs in dilating canine and porcine coronary microvessels (50-140 mum ID) and activating large-conductance Ca2+-activated K+ (BKCa) channels. The potencies and efficacies of EET regioisomers and enantiomers were compared with those of two EET homologs: epoxyeicosaquatraenoic acids (EEQs), which are made from eicosapentaenoic acid by the same cytochrome P-450 epoxygenase that generates EETs from arachidonic acid, and epoxydocosatetraenoic acids (EDTs), which are EETs that are two carbons longer. With EC50 values of 3-120 pM but without regio- or stereoselectivity, EETs potently dilated canine and porcine microvessels. Surprisingly, the EEQs and EDTs had comparable potencies and efficacies in dilating microvessels. Moreover, 50 nM 13,14-EDT activated the BKCa channels with the same efficacy as either 11,12-EET enantiomer at 50 nM. We conclude that coronary microvessels and BKCa channels possess low structural specificity for EETs and suggest that EEQs and EDTs may thereby also be endothelium-derived hyperpolarizing factors.
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