Free radicals-induced changes in mesenteric microvascular dimensions in the anesthetized cat.

Okabe, Eiichiro; Todoki, Kazuo; Odajima, Chisato; Itô, Haruo

doi:10.1254/jjp.33.1233

Cited by 9 publications

(2 citation statements)

References 29 publications

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“…Kontos and co‐workers (1984) showed that free radicals produced an irreversible vasodilatation in pial arterioles of cats, in vivo. Similar findings were obtained by Okabe et al (1983) in the cat mesenteric microcirculation. Xanthine oxidase‐derived radicals were shown by Wolin and Belloni (1985) to decrease tension in noradrenaline (NA) precontracted vessel rings.…”

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confidence: 89%

Inhibition by singlet molecular oxygen of the vascular reactivity in rabbit mesenteric artery

Mizukawa

Okabe

1997

British J Pharmacology

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1 The e ects of reactive oxygen intermediates derived from photoactivated rose bengal on the vascular reactivity have been evaluated in rabbit mesenteric artery ring preparations. The artery rings were exposed to xanthene dye rose bengal (50 nM) illuminated (6,000 lux) at 560 nm for 30 min. Spin trapping studies with 2,2,6,6-tetramethylpiperidine (TEMP) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) with electron spin resonance spectrometry were also conducted in solution (and not within tissues) to determine quantitatively the reactive oxygen species generated from photoactivated rose bengal. 2 Contraction of the ring preparations induced by noradrenaline (10 78 to 10 74 M) was attenuated by previous exposure to photolysed rose bengal; the observation that the pD 2 decreased without a signi®cant reduction in maximum tension generation is consistent with the view that receptor dysfunction may be involved in the e ect of photolysed rose bengal. 3 Prior exposure to photolysed rose bengal of the ring preparations inhibited the endotheliumdependent relaxation evoked by acetylcholine (10 76 M) and calcium ionophore A23187 (10 77 M), but not the endothelium-independent relaxation evoked by nitroglycerin (10 76 M). 4 A variety of scavengers, superoxide dismutase (33 units ml 71 ), catalase (32 units ml 71 ) and 1,3-dimethyl-2-thiourea (DMTU, 10 mM), which should eliminate the superoxide anion radical, H 2 O 2 and the hydroxyl radical, had no e ect on the attenuated responses to noradrenaline and acetylcholine induced by photolysed rose bengal. In contrast, the inhibition of the observed e ect of photolysed rose bengal was obtained with addition of histidine (25 mM), a singlet molecular oxygen quencher. 5 It was found that photolysis of rose bengal from a 1 : 2 : 2 : 1 quartet, characteristic of the hydroxyl radical-DMPO spin adduct, which was e ectively blunted by DMTU, superoxide dismutase and catalase whereas histidine was ine ective. The results of the electron spin resonance study also showed that a singlet molecular oxygen was produced by photoactivation of rose bengal; this was detected as singlet oxygen-TEMP product (TEMPO; 2,2,6,6-tetramethylpiperidine-N-oxyl). The formation of the TEMPO signal was strongly inhibited by histidine, but not by DMTU, superoxide dismutase and catalase. 6 It is suggested that the superoxide anion radical, H 2 O 2 and hydroxyl radical are formed in addition to singlet molecular oxygen, and the data obtained from the present study indicate that singlet molecular oxygen is one of the most destructive oxygen species. Endothelium-dependent relaxation is quite vulnerable to singlet molecular oxygen. Singlet oxygen also depresses noradrenaline-induced contraction possibly via a-adrenoceptor dysfunction. This, in turn, may lead to vascular incompetence.

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