title: Tubifex: a sensitive model for UV-B-induced phototoxicity.
abstract: The natural increase of UV-B radiation levels due to depletion of the ozone layer in the atmosphere may impose additional stress for the survival of zooplanktons which serve as a major constituent of the aquatic food chain. To study the adverse effects of UV-B radiation on the aquatic biomass, studies were conducted using the aquatic organism Tubifex as a model, as UV-B radiation is known to penetrate into the natural waters. UV-B radiation induced mortality in tubifex and the production of activated oxygen species by these organisms. Alterations in DNA, RNA, protein, glutathione (GSH), hydrogen peroxide H(2)O(2), thiobarbituric acid-reactive substance (TBA-RS), ATPase, AChE, GST, and LDH activities in Tubifex at various doses (0-2.0 J) of UV-B radiation were found. LC(50) value for UV-B-induced mortality of Tubifex was 0.80+/-0.15 J and the threshold dose was 0.35+/-0.05 J; mortality began within 3h postirradiation. UV-B dose-dependent production of singlet oxygen, superoxide anion, and hydroxyl radicals by Tubifex was observed. DNA, RNA, protein, and GSH contents were found to decrease significantly (P<0.001) while H(2)O(2) and TBA-RS increased (P<0.01) under the influence of UV-B radiation. The activities of ATpase, AChE, and GST enzymes were inhibited (P<0.01) and LDH activity was significantly increased (P<0.001) in Tubifex exposed to UV-B radiation. The results suggest that an increase in UV-B radiation alters several biochemical processes, leading to the mortality of the organism. Tubifex could be useful as a sensitive alternate model for studying UV-B-induced phototoxicity and possible mechanisms of action.
authors.affiliation: Photobiology Division, Industrial Toxicology Research Centre, Lucknow, India.
authors.forename: R B
authors.initials: RB
authors.lastname: Misra
authors.forename: G Suresh
authors.initials: GS
authors.lastname: Babu
authors.forename: R S
authors.initials: RS
authors.lastname: Ray
authors.forename: R K
authors.initials: RK
authors.lastname: Hans
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D004249:DNA Damage; D020387:Food Chain; D005978:Glutathione / Q000032:analysis; D007928:Lethal Dose 50; D008962:Models, Theoretical; D009835:Oligochaeta / Q000502:physiology*; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000032:analysis; D014466:Ultraviolet Rays / Q000009:adverse effects*; D015048:Zooplankton
chemical_list: D011506:Proteins; D012313:RNA; D005978:Glutathione