Synergistic effect of UVB radiation and age on HMPS enzymes in rat lens homogenate.
The behaviour of rat lenticular enzymes, glucose-6-phosphate dehydrogenase (G6PD, EC: 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGD, EC: 1.1.1.44) as a function of age and UVB irradiation (in vitro) was investigated by irradiating the lens homogenate from 3- and 12-month-old rats at 300 nm (100 microW cm-2). In the 3-month-old group the specific activities of G6PD and 6PGD were reduced by 26% and 42%, respectively, after 24 h of irradiation, whereas in the 12-month-old group the decrease was 38% and 49% respectively, which suggests that the susceptibility of HMPS enzymes to UVB damage is higher in older lenses. The decrease in specific activity was associated with a change in apparent K(m) and Vmax (marginal in 3 months and significant in 12 months) of these enzymes due to UVB irradiation. UVB irradiation also decreased the levels of NADPH and NADPH/NADP ratio. These changes, altered activities of G6PD and 6PGD and altered levels of NADPH, may in turn have a bearing on lens transparency.
Reddy
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GB
Laboratory of Ocular Biochemistry, National Institute of Nutrition, Hyderabad, India. bhanu@mbu.iisc.ernet.in
Bhat
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KS
D000375:Aging / Q000378:metabolism / Q000528:radiation effects*; D000818:Animals; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D007908:Lens, Crystalline / Q000201:enzymology* / Q000528:radiation effects*; D008297:Male; D009249:NADP / Q000378:metabolism; D010427:Pentose Phosphate Pathway / Q000528:radiation effects*; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014466:Ultraviolet Rays
D009249:NADP; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase