Phosphorus-31 NMR study of the effects of UV on squirrel lenses

In a series of 31P NMR experiments the effects of near-UV radiation on the phosphorus metabolites in pigmented lenses from grey squirrels were studied; UV radiation ranged from 300 to 400 nm, peaking at 365 nm. Squirrels were killed, intact lenses removed, exposed to UV, put in an NMR perfusion cell, and 31P NMR spectra were recorded. In vitro exposure of squirrel lenses for periods ranging from 4 to 22 hr were made. ATP levels, as measured by NMR, decreased as the radiation dose increased. For a 22-hr exposure (121 J cm-2) ATP levels decreased by 67% relative to control values. At lower dose levels there was a correspondingly smaller decrease in ATP levels. Histological examination showed UV-irradiated lenses had disrupted epithelium, loss of attachment to cortical fiber cells and fluid accumulation under the capsule. It is clear that lenticular exposure to near-UV, predominantly at 365 nm (UV-A), does cause metabolic deterioration through degradation of normal ATP energy levels. The grey squirrel pigmented lens strongly absorbs near-UV radiation which enhances the observed metabolic changes and observed opacities. The results demonstrate the utility of using 31P NMR to evaluate metabolic changes associated with near-UV irradiation.