Pathophysiological and molecular pharmacological studies on the role of reactive oxygen species in disorder of circulatory function.

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The level of superoxide production was investigated by measuring lucigenin chemiluminescence signals in rabbit saphenous arteries with and without endothelium. Phorbol 12, 13-dibutirate (PDBu), an activator of protein kinase C (PKC), increased the chemiluminescence signals in preparations with and without endothelium. Under the conditions, superoxide dismutase(SOD) greatly attenuated the chemiluminescence signals. Each GF109203 (a selective inhibitor of PKC) and diphenylene iodochloride [an inhibitor of NAD (P) H oxidase] inhibited the chemiluminescence signals. These results suggest that an activation of NAD (P) H by PKC enhances generation of superoxide in vascular smooth muscle cells (and possibly in endothelial cells).Superoxide generated by hypoxanthine + xanthine oxidase inhibited the contraction induced by noradrenaline (NAd) in endothelium-denuded strips of rabbit mesenteric arteries. This superoxide-induced response was enhanced by SOD, but this was inhibited by catalase or as … More corbic acid. These results suggest that under physiological conditions, SOD breaks down superoxide to H_2O_2 that inhibits the NAd-induced contraction in vascular smooth muscles.H_2O_2 hyperpolarized smooth muscle cell membrane, which was inhibited by diclofenac sodium (an inhibitor of cyclooxygenase), and by glibenclamide (an inhibitor of K_<ATP> channels). These results suggest that H_2O_2 increases the synthesis of prostaglandins that hyperpolarizes the smooth muscle cell membrane through an activation of K_<ATP> channels. It is also suggested that the H_2O_2-induced membrane hyperpolarization plays an important role on the H_2O_2-induced relaxation on NAd-contraction in rabbit mesenteric artery.In β-escin-skinned smooth muscles of rabbit mesenteric arteries, NAd plus GTP enhanced the contraction induced by 0.3 μM Ca^<2+>. H_2O_2 had no effect on the Ca^<2+>-contraction in the presence and absence of NAd plus GTP, suggesting that H_2O_2 has no direct action on the Ca^<2+>-sensitivity of contractile proteins in vascular smooth muscles of rabbit mesenteric artery. Less