11(R),12(S),15(S)-trihydroxyeicosa-5(Z),8(Z),13(E)-trienoic acid: an endothelium-derived 15-lipoxygenase metabolite that relaxes rabbit aorta.
Previous studies indicate that 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA), an endothelium-derived hyperpolarizing factor in the rabbit aorta, mediates a portion of the relaxation response to acetylcholine by sequential metabolism of arachidonic acid by 15-lipoxygenase, hydroperoxide isomerase, and epoxide hydrolase. To determine the stereochemical configuration of the endothelial 11,12,15-THETA, its activity and chromatographic migration were compared with activity and migration of eight chemically synthesized stereoisomers of 11,12,15(S)-THETA. Of the eight isomers, only 11(R),12(S),15(S)-trihydroxyeicosa-5(Z),8(Z),13(E)-trienoic acid comigrated with the biological 11,12,15-THETA on reverse- and normal-phase HPLC and gas chromatography. The same THETA isomer (10(-7)-10(-4) M) relaxed the rabbit aorta in a concentration-related manner (maximum relaxation = 69 +/- 5%). These relaxations were blocked by apamin (10(-7) M), an inhibitor of small-conductance Ca2+-activated K+ channels. In comparison, 11(S),12(R),15(S),5(Z),8(Z),13(E)-THETA (10(-4) M) relaxed the aorta by 22%. The other six stereoisomers were inactive in this assay. With use of the whole cell patch-clamp technique, it was shown that 10(-4) M 11(R),12(S),15(S),5(Z),8(Z),13(E)-THETA increased outward K+ current in isolated aortic smooth muscle cells by 119 +/- 36% at +60 mV, whereas 10(-4) M 11(R),12(R),15(S),5(Z),8(Z),13(E)-THETA increased outward K+ current by only 20 +/- 2%. The 11(R),12(S),15(S),5(Z),8(Z),13(E)-THETA-stimulated increase in K+ current was blocked by pretreatment with apamin. These studies suggest that 11(R),12(S),15(S)-trihydroxyeicosa-5(Z),8(Z),13(E)-trienoic acid is the active stereoisomer produced by the rabbit aorta. It relaxes smooth muscle by activating K+ channels. The specific structural and stereochemical requirements for K+ channel activation suggest that a specific binding site or receptor of 11,12,15-THETA is involved in these actions.
Gauthier
Kathryn M
KM
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA. kgauth@mcw.edu
Chawengsub
Yuttana
Y
Goldman
Daniel H
DH
Conrow
Raymond E
RE
Anjaiah
Siddam
S
Falck
J R
JR
Campbell
William B
WB
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001030:Apamin / Q000494:pharmacology; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003627:Data Interpretation, Statistical; D004730:Endothelium, Vascular / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D066298:In Vitro Techniques; D007536:Isomerism; D008564:Membrane Potentials / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists; D011817:Rabbits; D013237:Stereoisomerism; D014665:Vasodilator Agents / Q000737:chemistry / Q000494:pharmacology*
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D014665:Vasodilator Agents; D001030:Apamin; C066049:11,12,15-trihydroxyeicosatrienoic acid; D001093:Arachidonate 15-Lipoxygenase; D015126:8,11,14-Eicosatrienoic Acid