Metabolic changes during cataract formation by ultraviolet radiation in the incubated rabbit lens.

Abstract

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.