title: [Ascorbate free radical reductase activity in vertebrate lenses of some species].
abstract: OBJECTIVE
  To clarify the function of ascorbate free radical (AFR) reductase in the lens antioxidation mechanism, we investigated the difference among species in AFR reductase activity in different vertebrate lenses.
  
  
  METHODS
  Soluble and insoluble fractions were prepared from the lenses of frogs, guinea pigs, rats, rabbits, pigs, and calves. AFR reductase and diaphorase activity of each fraction was determined.
  
  
  RESULTS
  AFR reductase activity in the lens soluble fraction was the highest in frogs. That of guinea pigs and rabbits was at the next level; there was only a little activity in rats and pigs, and none was detected in calves. Membrane-bound AFR reductase in the lens insoluble fraction was extracted by 0.3% Triton X-100. The membrane-bound enzyme activity was almost at the same level in frogs, rats, rabbits, and calves, and a little higher in guinea pigs and pigs. However, such species-specificity of AFR reductase activity as in the soluble fraction was not observed in 0.3% Triton X-100 extracts. Diaphorase activity was 3 to 9 times as much as AFR reductase activity in the soluble fractions of frogs, guinea pigs, and rabbits, but in 0.3% Triton X-100 extracts of all vertebrate species used, it was very high, 108 to 311 times the AFR reductase activity.
  
  
  CONCLUSIONS
  These results suggest that the lens soluble and membrane-bound AFR reductases are individual enzyme molecules and have different antioxidative functions. The lenses of frogs, guinea pigs, and rabbits contain a near-ultraviolet (UV) light absorbing compound, reduced pyridine nucleotide at a high concentration. Therefore, the soluble AFR reductase activity may be high in the vertebrate lenses with a near-UV light filter, and enhance the antiphotoxidation of ascorbic acid.
authors.affiliation: Department of Ophthalmology, Tokai University Tokyo Hospital, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Matsukura
authors.forename: M
authors.initials: M
authors.lastname: Bando
authors.forename: H
authors.initials: H
authors.lastname: Obazawa
authors.forename: M
authors.initials: M
authors.lastname: Oka
authors.forename: M
authors.initials: M
authors.lastname: Takehana
mesh_terms: D000818:Animals; D002417:Cattle; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D006168:Guinea Pigs; D007908:Lens, Crystalline / Q000201:enzymology* / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D011817:Rabbits; D011892:Rana catesbeiana; D051381:Rats; D017208:Rats, Wistar; D013045:Species Specificity; D013552:Swine
chemical_list: D009243:NAD; D009249:NADP; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); D008058:Dihydrolipoamide Dehydrogenase