Endothelial and myogenic regulation of coronary artery tone in the mouse

Ventricular septal (150–200 μm) arteries were isolated from the hearts of six-week-old CD-1 mice and mounted on a pressure myograph. Equilibration of the vessels at 70 mm Hg for 60 min resulted in the development of spontaneous myogenic tone. Maximum tone observed in these vessels greatly exceeded that previously reported in septal arteries from rats. Inhibition of endothelin ET A and endothelin ET B receptors with bosentan (1 and 10 μM) reduced basal tone. Endothelin release required intact endothelial cells. The α 1-adrenceptor selective agonists phenylephrine and methoxamine did not cause change in coronary tone, while the α 2-adrenceptor selective agonists 6-allyl-2-amino5,6,7,8-tetrahydro-4 H-thiazolo-[4,5-d]azepin-dihydrochloride (BHT 920) and clonidine produced vasodilatation. Noradrenaline (1 nM–10 μM) induced a concentration-dependent vasodilatation, which was inhibited by concurrent treatment with yohimbine (10 μM) and propranolol (20 μM). Vasodilatation due to BHT 920 was abolished with vessel denudation, indicating the endothelial location of α 2-adrenoceptors. Acetylcholine (1 nM–10 μM) caused an endothelium dependent vasodilatation; inhibition of nitric oxide synthase with N ω-nitro- l-arginine methyl ester attenuated this response. The endothelium-dependent vasodilators bradykinin and substance P produced no vasomotor effect in mouse coronary arteries. Differences between human and murine responses may impact on the relevance of the mouse coronary artery for use as a potential model of human coronary vessel diseases.