title: Antihypertensive potential and mechanism of action of astaxanthin: II. Vascular reactivity and hemorheology in spontaneously hypertensive rats.
abstract: The current study was designed to determine the effects of a dietary astaxanthin (ASX-O) on vascular reactivity in spontaneously hypertensive rats (SHR), in order to verify its antihypertensive action mechanism. We evaluated contractions induced by phenylephrine (Phe), angiotensin II (Ang II) and the xanthine/xanthine oxidase (Xan/XOD) system, and relaxations induced by sodium nitroprusside (SNP) as well as endothelium-dependent relaxations mediated by acetylcholine (ACh) in thoracic aorta of the SHR, with and without ASX-O intervention. We also investigated the effects of ASX-O on blood rheology using a microchannel array system. In this study, ASX-O showed a significant modulatory effect on nitric oxide (NO)-induced vasorelaxation by the NO-donor SNP (p<0.05). However, it did not show significant effects in restoring the impaired endothelium-dependent relaxation to ACh in the SHR. On the other hand, the constrictive effects by Phe, Ang II and Xan/XOD were ameliorated by ASX-O (p<0.05). ASX-O also demonstrated significant hemorheological effect by decreasing the microchannel transit time of whole blood. In conclusion, the results suggest that ASX-O may act in modulating the blood fluidity in hypertension, and that the antihypertensive effects of ASX-O may be exerted through mechanisms including normalization of the sensitivity of the adrenoceptor sympathetic pathway, particularly [alpha]-adrenoceptors, and by restoration of the vascular tone through attenuation of the Ang II- and reactive oxygen species (ROS)-induced vasoconstriction.
authors.affiliation: International Research Center for Traditional Medicine, Toyama Prefecture, Japan. ghazihussein@hotmail.com
authors.forename: Ghazi
authors.initials: G
authors.lastname: Hussein
authors.forename: Hirozo
authors.initials: H
authors.lastname: Goto
authors.forename: Shinobu
authors.initials: S
authors.lastname: Oda
authors.forename: Tomomi
authors.initials: T
authors.lastname: Iguchi
authors.forename: Ushio
authors.initials: U
authors.lastname: Sankawa
authors.forename: Kinzo
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D018056:Hemorheology / Q000379:methods*; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000959:Antihypertensive Agents; D024341:Xanthophylls; D019207:beta Carotene; C005948:astaxanthine