Amlodipine attenuates oxidative stress-induced hypertension

Background: Dihydropyridine Ca2+-blockers, frequently used as antihypertensive and antianginal agents, have been found to exert potent antioxidant and cytoprotective activities against free radical-mediated vascular injury. Methods: In the current study we examined the effect of amlodipine (AMLOD) on oxidative stress-induced hypertension in Sprague-Dawley rats administered buthionine-sulfoximine (BSO), a glutathione (GSH) synthase inhibitor, in the drinking water. The control animals received drug-free water. Blood pressure (BP) was measured by tail-cuff plethysmography. Plasma levels of total 8-isoprostane, thromboxane A(2), prostacyclin, nitric oxide, and aortic cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were determined by enzyme immunoassay. Plasma, kidney, and heart GSH were analyzed by high-performance liquid chromatography. Results: Administration of BSO significantly increased BP, isoprostane, and thromboxane A(2), whereas GSH, PGI(2), and cAMP were reduced. When given alone, AMLOD alone reduced BP and the plasma levels of isoprostane and thromboxane A(2), and elevated prostacyclin, nitric oxide, cGMP, and cAMP. When administered with BSO, AMLOD reversed the BSO-induced elevation of BP, isoprostane, and thromboxane A(2) as well as the reduction in prostacyclin, cAMP, and cardiac GSH levels. Conclusions: The antihypertensive effect of amlodipine involves a reduction in oxidative stress, which appears to be mediated in part by the prostanoid endothelium-derived factors and nitric oxide. (C) 2004 American Journal of Hypertension, Ltd.