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Updated: Aug 15, 2026
Measurement of Endothelium-Dependent Vasorelaxation in the Mouse Thoracic Aorta Using Tensometric Small Volume Chamber Myography
Published on: August 12, 2022
Reticulocyte 15-lipoxygenase-I is important in acetylcholine-induced endothelium-dependent vasorelaxation in rabbit
Xin Tang1, Blythe B Holmes, Kasem Nithipatikom
1Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Objective:
Aortic 15-lipoxygenase (15-LO) metabolizes arachidonic acid (AA) to 15-hydroperoxyeicosatetraenoic acid, which is then converted to the vasodilators 15-hydroxy-11,12-epoxyeicosatrienoic acid and 11,12,15-trihydroxyeicosatrienoic acid. These metabolites contribute to endothelium-dependent relaxations of rabbit aorta to AA and acetylcholine. We investigated the identity of rabbit aortic 15-LO and studied its importance in the regulation of vascular tone.
Methods And Results:
RT-PCR using 12-lipoxygenase/15-LO specific primers resulted in a 572-bp product with a sequence identical to 15-LO-I from rabbit aorta. A RT-PCR/restriction digest strategy excluded expression of 12-lipoxygenase. Immunoblotting revealed 15-LO-I expression in rabbit endothelial and smooth muscle cells. Aortic homogenates and cytosolic fractions metabolize AA to 15(S)-hydroxyeicosatetraenoic acid and linoleic acid to 13(S)-hydroxyoctadecadienoic acid. This activity was blocked by LO inhibitors. The kinetic characteristics (Michaelis constant of aortic 15-LO is 2.2+/-0.3 micromol/L for AA and 23.5+/-3.3 micromol/L for linoleic acid) of aortic 15-LO were similar to those of the purified 15-LO-I. An antisense oligonucleotide inhibited 15-LO-I expression in rabbit aorta. Indomethacin and nitro-L-arginine-resistant relaxations to acetylcholine were inhibited by 15-LO-I antisense oligonucleotide but not by the scrambled oligonucleotide.
Conclusions:
15-LO-I is expressed in rabbit aortic endothelium and is important in endothelium-dependent regulation of vascular tone.
