title: Early effects of acute gamma-radiation on vascular arterial tone.
abstract: 1. To determine the acute effects of irradiation on the functionality of vessel, rat aortic rings were mounted in an organ bath for isometric tension measurements and irradiated (60Co, 1 Gy min(-1), 15 min). 2. Irradiation, which is without effect on non-contracted or endothelium-denuded vessels, led to an immediate and reversible increase in vascular tone on (-)-phenylephrine (1 microM)-precontracted aortic rings. The tension reached a plateau about 5 min after the beginning of irradiation. 3. The maximal radiation-induced contraction occurred on aortic rings relaxed by acetylcholine (ACh) (1 microM). In this condition, the addition of catalase (1000 u ml(-1)), which reduces hydrogen peroxide, and DMSO (0.1% v/v), which scavenges hydroxyl radical, had no influence on tension level while superoxide dismutase (SOD) (100 u ml(-1)), a superoxide anion scavenger, reduced the observed contraction. A similar result was obtained in the presence of indomethacin (10 microM), a cyclo-oxygenase blocker. 4. Pretreatment of rings with the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (10-100 microM) inhibited the radiation-induced contraction. 5. This effect was dose rate-dependent and even occurred for a very low dose rate (0.06 Gy min(-1)). 6. The present results indicate that gamma-radiation induces an instantaneous vascular tone increase that is endothelium and dose rate-dependent. This effect is (i) maximal when nitric oxide (NO) is produced, (ii) greatly reduced by SOD and (iii) inhibited by L-NAME, suggesting a major involvement of complexes between NO and superoxide anion.
authors.affiliation: Université Joseph Fourier, Grenoble, France.
authors.forename: V
authors.initials: V
authors.lastname: Bourlier
authors.forename: M
authors.initials: M
authors.lastname: Diserbo
authors.forename: M
authors.initials: M
authors.lastname: Joyeux
authors.forename: C
authors.initials: C
authors.lastname: Ribuot
authors.forename: E
authors.initials: E
authors.lastname: Multon
authors.forename: P
authors.initials: P
authors.lastname: Gourmelon
authors.forename: J
authors.initials: J
authors.lastname: Verdetti
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000378:metabolism / Q000528:radiation effects*; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals; D005720:Gamma Rays; D007213:Indomethacin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000528:radiation effects*; D009569:Nitric Oxide / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D005609:Free Radicals; D009569:Nitric Oxide; D007213:Indomethacin