Blood and aqueous humour antioxidants in cataractous poodles.
BACKGROUND
Cataract is an important cause of blindness in dogs and frequently develops in young animals of certain breeds, such as the English cocker spaniel and the poodle. Protein oxidation is one of the mechanisms involved in lens opacification and may be causally related to depleted or diminished endogenous antioxidant defences. We evaluated the levels of enzymatic and nonenzymatic antioxidants in blood and aqueous humour of cataractous poodles in comparison to noncataractous poodles.


METHODS
We studied 35 cataractous poodles aged 2 to 11 years, 14 noncataractous poodles and 15 noncataractous mixed-breed dogs. The activity of erythrocyte antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase [G6PD]) was evaluated in 18 cataractous poodles and 14 noncataractous poodles. We evaluated ascorbic acid levels in plasma of all animals and in aqueous humour of cataractous poodles and mixed-breed dogs. The dogs were deprived of food for 12 hours before sampling. Blood samples were obtained from the jugular vein before and during anesthesia. Aqueous humour samples were obtained just before the anterior chamber was opened.


RESULTS
The activity of superoxide dismutase, G6PD and catalase was significantly higher in noncataractous poodles than in cataractous poodles (p < or = 0.05). The activity of glutathione peroxidase was lower in noncataractous poodles than in cataractous poodles, but not significantly so. There was no difference in mean plasma ascorbic acid concentration between cataractous poodles (21.3 microM [standard deviation (SD) 7.4 microM]), noncataractous poodles (21.6 microM [SD 7.4 microM]) and non-cataractous mixed-breed dogs (25.8 microM [SD 7.5 microM]). Similarly, there was no difference in mean aqueous humour ascorbic acid concentration between cataractous poodles (191.7 microM [SD 62.0 microM] and noncataractous mixed-breed dogs (215.7 microM [SD 91.8 microM]).


CONCLUSIONS
The results indicate that, at least in the population studied here, no correlation exists between the onset of cataract and ascorbic acid concentration in blood and aqueous humour. The decreased activity of antioxidant enzymes may explain in part the onset of cataract in poodles.
Barros
Paulo S M
PS
Serviço de Oftalmologia, Departamento de Cirurgia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil. pauloeye@usp.br
Safatle
Angelica M V
AM
Queiroz
Lelio
L
Silva
Vanessa V
VV
Barros
Silvia B M
SB
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001082:Aqueous Humor / Q000201:enzymology*; D001205:Ascorbic Acid / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002386:Cataract / Q000201:enzymology / Q000662:veterinary*; D002387:Cataract Extraction; D004283:Dog Diseases / Q000201:enzymology*; D004285:Dogs; D004910:Erythrocyte Membrane / Q000201:enzymology*; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism
D000975:Antioxidants; D010088:Oxidoreductases; D005954:Glucosephosphate Dehydrogenase; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D001205:Ascorbic Acid