title: Photochemical formation of hydroxyl radicals in tissue extracts of the coral Galaxea fascicularis.
abstract: Various stresses induce the formation of reactive oxygen species (ROS) in biological cells. In addition to stress-induced ROS, we studied the photochemical formation of hydroxyl radicals (˙OH), the most potent ROS, in coral tissues using phosphate buffer-extracted solutions and a simulated sunlight irradiation system. ˙OH formation was seen in extracts of both coral host and endosymbiont zooxanthellae. This study is the first to report quantitative measurements of ˙OH photoformation in coral tissue extracts. Our results indicated that whether or not coral bleaching occurred, coral tissues and symbiotic zooxanthellae have the potential to photochemically produce ˙OH under sunlight. However, no significant difference was found in the protein content-normalized formation rates of ˙OH between corals incubated under different temperatures and irradiance conditions. ˙OH formation rates were reduced by 40% by reducing the UV radiation in the illumination. It was indicated that UV radiation strongly affected ˙OH formation in coral tissue and zooxanthellae, in addition to its formation through photoinhibition processes.
authors.affiliation: Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara-cho, Okinawa, Japan. tomi_higuchi@hotmail.com
authors.forename: Tomihiko
authors.initials: T
authors.lastname: Higuchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fujimura
authors.forename: Yuya
authors.initials: Y
authors.lastname: Hitomi
authors.forename: Takemitsu
authors.initials: T
authors.lastname: Arakaki
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Oomori
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000378:metabolism* / Q000528:radiation effects*; D004141:Dinoflagellida / Q000378:metabolism / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D038761:Photobleaching / Q000528:radiation effects; D055668:Photochemical Processes; D017382:Reactive Oxygen Species / Q000378:metabolism; D013472:Sunlight / Q000009:adverse effects; D013559:Symbiosis
chemical_list: D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D007501:Iron