Submitted on September 7, 2007
Accepted on March 25, 2008
Cytochrome P450 metabolites of 2-Arachidonoyl Glycerol play a Role in Ca2+-induced Relaxation of Rat Mesenteric Arteries
Emmanuel M Awumey1*, Sylvie K Hill1, Debra I. Diz2, and Richard Dean Bukoski3
1 Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, United States
2 Hypertension & Vascular Disease Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States
3 Biomed/Biotech Research Institute, North Carolina Central University, 700 George Street, Durham, North Carolina, 27707, United States
* To whom correspondence should be addressed. E-mail: eawumey{at}nccu.edu.
The perivascular sensory nerve (PvN) Ca2+-sensing receptor (CaR) is implicated in Ca2+-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries, which involves the vascular endogenous cannabinoid system. We determined the effect of inhibition of diacylglycerol (DAG) lipase (DAGL), phospholipase A2 (PLA2) and Cytochrome P450 (CYP) on Ca2+-induced relaxation of PE-contracted rat mesenteric arteries. Our findings indicate that Ca2+-induced vasorelaxation is not dependent on the endothelium. The DAGL inhibitor, RHC 802675 (1 µM) and the CYP and PLA2 inhibitors, quinacrine (5 µM) (EC50: RHC 802675, 2.8 ±0.4 mM vs. Control, 1.4 ± 0.3 mM; Quinacrine, 4.8 ± 0.4 vs. Control, 2.0 ± 0.3 mM; n = 5) as well as AACOCF3 (1 µM) reduced Ca2+-induced relaxation of mesenteric arteries. Synthetic 2-arachidonoyl glycerol (2-AG) and glycerated epoxyeicosatrienoic acids (GEETs) induced concentration-dependent relaxation of isolated arteries. 2-AG relaxations were blocked by iberiotoxin (IBTx) (EC50: Control, 0.96 ±0.14 nM; IBTx, 1.3 ±0.5 µM) and miconazole (48 ±3%), and 11,12-GEET responses were blocked by IBTx (EC50: Control = 55 ± 9 nM; IBTx = 690 ± 96 nM) and SR141716A. The data suggest that activation of the CaR in the PvN network by Ca2+e leads to synthesis and/or release of metabolites of the CYP epoxygenase pathway and metabolism of DAG to 2-AG, and subsequently to GEETs. The findings indicate a role for 2-AG and its metabolites in Ca2+-induced relaxation of resistance arteries therefore this receptor may be a potential target for the development of new vasodilator compounds for anti-hypertensive therapy.
