15-Lipoxygenase metabolites contribute to age-related reduction in acetylcholine-induced hypotension in rabbits.

Abstract

Arachidonic acid (AA) metabolites from the 15-lipoxygenase-1 (15-LO-1) pathway, trihydroxyeicosatrienoic acids (THETAs) and hydroxy-epoxyeicosatrienoic acids (HEETAs), are endothelium-derived hyperpolarizing factors (EDHFs) and relax rabbit arteries. Rabbit vascular 15-LO-1 expression, THETA and HEETA synthesis, and nitric oxide and prostaglandin-independent relaxations to acetylcholine (ACh) and AA decreased with age (neonates to 16-wk-old). We characterized age-dependent ACh-hypotensive responses in vivo in 1-, 4-, 8-, and 16-wk-old rabbits and the contribution of THETAs and HEETAs to these responses. In anesthetized rabbits, blood pressure responses to ACh (4-4,000 ng/kg) were determined in the presence of vehicle or various inhibitors. ACh responses decreased with age (P > 0.001). In the absence or presence of N(omega)-nitro-l-arginine methyl ester (l-NAME) and indomethacin (Indo), maximum responses in 1 (-54.7 +/- 7.4 and -37.9 +/- 3.9%)- and 4 (-48.8 +/- 2.4 and -35.5 +/- 7.8%)-wk-old rabbits were higher than 8 (-30.0 +/- 2.8 and -26.6 +/- 4.4%)- and 16 (-36.7 +/- 3.5 and -27.3 +/- 10%)-wk-old rabbits. A lipoxygenase inhibitor, BW755C, reduced THETA and HEETA synthesis in mesenteric arteries. In the presence of Indo and N(omega)-nitro-l-arginine, ACh relaxations were reduced by BW755C to a greater extent in the mesenteric arteries from the younger rabbits. In 4-wk-old rabbits treated with l-NAME and Indo, the maximum ACh hypotension was reduced by the potassium channel inhibitors apamin and charybdotoxin to -6.9 +/- 0.9%, by apamin alone to -19.5 +/- 1.4%, and by BW755C to -18.8 +/- 3.5%. The present study indicates that the age-related decrease in ACh-induced hypotension is mediated by the decreased synthesis of the 15-LO-1 metabolites THETAs and HEETAs.

• Authors: Nitin T Aggarwal, Kathryn M Gauthier, William B Campbell
• Journal: American journal of physiology. Heart and circulatory physiology (Am J Physiol Heart Circ Physiol) Vol. 295 Issue 1 Pg. H89-96 (Jul 2008) ISSN: 0363-6135 [Print] United States
• PMID: 18456739 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Cyclooxygenase Inhibitors
• Eicosanoids
• Lipoxygenase Inhibitors
• Potassium Channel Blockers
• Vasodilator Agents
• Charybdotoxin
• Apamin
• 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine
• Arachidonate 15-Lipoxygenase
• Nitric Oxide Synthase
• Acetylcholine
• NG-Nitroarginine Methyl Ester
• Indomethacin

Topics

• 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine (pharmacology)
• Acetylcholine (pharmacology)
• Age Factors
• Aging
• Animals
• Apamin (pharmacology)
• Arachidonate 15-Lipoxygenase (metabolism)
• Blood Pressure (drug effects)
• Charybdotoxin (pharmacology)
• Cyclooxygenase Inhibitors (pharmacology)
• Dose-Response Relationship, Drug
• Eicosanoids (metabolism)
• Hypotension (metabolism, physiopathology)
• In Vitro Techniques
• Indomethacin (pharmacology)
• Lipoxygenase Inhibitors (pharmacology)
• Mesenteric Arteries (drug effects, enzymology, metabolism)
• NG-Nitroarginine Methyl Ester (pharmacology)
• Nitric Oxide Synthase (antagonists & inhibitors, metabolism)
• Potassium Channel Blockers (pharmacology)
• Rabbits
• Vasodilation (drug effects)
• Vasodilator Agents (pharmacology)