Proton pump inhibitors omeprazole and lansoprazole induce relaxation of isolated human arteries

Vasorelaxant effects of H +/K +-ATPase were previously demonstrated in artery rings isolated from experimental animals. We examined the effects of clinically used H +/K +-ATPase inhibitors on isolated human internal mammary ( n = 19) and radial ( n = 5) arteries. Omeprazole and lansoprazole (30–300 μM) both induced concentration-dependent, reversible and reproducible relaxations of arteries which were precontracted with phenylephrine (5 μM), histamine (15 μM), high K + (80 mM), ouabain (1 μM) and K + free solution. Relaxant responses were similar in both arteries. Presence of N ω-Nitro- l-arginine methyl ester (30 μM) had no effect on lansoprazole-induced responses, thus relaxations are independent from nitric oxide. Relaxation in the K + free medium implies that this action could not be due to the inhibition of H +/K +-ATPase. Lansoprazole (300 μM) inhibited Ca 2+-induced contractions in high K +-Ca 2+ free medium. Omeprazole and lansoprazole may act on a common mechanism which plays a crucial role in regulating human vascular tone and that mechanism appeared to be involved in the regulation of intracellular Ca 2+.