Cyclo-oxygenase inhibition restores the attenuated vasodilation in manganese-deficient rat aorta

Previously we showed that manganese (Mn) deficiency enhances the arterial contractile response to alpha(1) adrenergic stimuli and affects vasomotor tone. The aim of this study was to test the hypothesis that dietary Mn deficiency inhibits the vasodilation pathways of rat aorta. Vascular ring studies were conducted in aortic rings from weanling male Sprague-Dawley rats that were fed either a Mn deficient (MnD) or a Mn adequate/control diet (MnA) (<1 and 12 mg/kg Mn, respectively) for a 14-wk period. We investigated endothelium-dependent vasodilation induced by acetylcholine (Ach; 10(-8) to 3 x 10(-6) mol/L) in isolated 3-mm aortic rings precontracted with l-phenylephrine (l-Phe; 10(-6) mol/L). Seven concentrations of Ach were used in the presence or absence of inhibitors of nitric oxide synthase and cyclo-oxygenase. After a second precontraction, 8 doses of sodium nitroprusside (SNP; 10(-8) to 10(-5) mol/L) were added to assess endothelium-independent vasodilation. We observed a decrease in Ach-induced and SNP-induced vasodilation in MnD rat aortas when compared with MnA rat aortas (P