RESUMO
We studied the energy metabolism of cataracts induced by ultraviolet (UV) irradiation by observing metabolic changes in lenses using 31P-, 1H-, and 13C-nuclear magnetic resonance (NMR) spectroscopy. % of hexose monophosphate shunt flux activity increased over time. The lactate/glucose ratio in the UV irradiation group decreased to about half of that of the corresponding control group (11.6 +/- 2.0% vs. 20.7 +/- 1.7%, respectively, p < 0.05) after 10 h of irradiation and to about 30% of that of the control group (25 +/- 2% vs. 92 +/- 6%, respectively) after 24 h. The adenosine triphosphate (ATP) level significantly decreased after 3 h of irradiation (86 +/- 29%, p < 0.05) and continuously decreased to 68 +/- 33% (p < 0.01) after 10 h of irradiation and 26 +/- 2% (p < 0.01) after 24 h of irradiation. Conversely, a significant increase in inorganic phosphate (Pi) was observed after 1 h of irradiation (111 +/- 26%, p < 0.05), and the Pi level gradually increased to 140 +/- 28% after 10 h of irradiation (p < 0.01) and 207 +/- 26% after 24 h (p < 0.01). A significant decrease in alpha-glycerophosphate was noted after 24 h (38 +/- 13%, p < 0.01). The ribose-5-phosphate (R-5-P) level gradually increased after irradiation to 128 +/- 13% (p < 0.05) after 10 h and 141 +/- 21% after 24 h (p < 0.01). The results suggest that of these metabolic changes a marked decline in glycolytic production of ATP, which inhibits membrane metabolism, may be an important cataract-inducing factor following UV irradiation.
