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Metabolic Changes in Rat Lens after In Vivo Exposure to Ultraviolet Irradiation: Measurements by High Resolution MAS ¹H NMR Spectroscopy

¹From the Faculties of Natural Sciences and Technology and ²Medicine, The Norwegian University of Science and Technology, Trondheim, Norway; and ³St. Erik’s Eye Hospital, Karolinska Institutet, Stockholm, Sweden.

PURPOSE. In the present study, high-resolution magic angle spinning proton nuclear magnetic resonance (HR-MAS ¹H NMR) spectroscopy was used to investigate changes in the metabolic profile of intact rat lenses after UVB irradiation of the eyes.

METHODS. Three groups of Sprague-Dawley rats were exposed to UVB radiation at 2.5, 5.0, and 7.5 kJ/m². One eye was exposed, and the contralateral eye served as the control. One week after exposure, the lenses were removed and forward light-scattering was quantified. Thereafter, proton NMR spectra from the intact lenses were obtained. Relative changes in metabolite concentrations were determined.

RESULTS. The lenses in all three groups showed significant increases in light-scattering after UVB irradiation. The high-quality HR-MAS ¹H NMR spectra permitted more than 30 different metabolites to be identified. UVB irradiation caused a significant decrease (P < 0.05) in concentrations of taurine, hypotaurine, tyrosine, phenylalanine, valine, myo-inositol, phosphocholine, betaine, succinate, and glutathione at all three UV doses. For glycine, glutamate, and lactate, significant decreases in concentration were observed at the two lowest UVR-B doses. The total amount of adenosine tri- and diphosphate and (ATP, ADP) decreased significantly and that of adenosine monophosphate AMP increased significantly at the two highest doses. Alanine was the only amino acid that increased after UVB irradiation. None of these metabolites exhibited a significant UVB dose-dependent relationship.

CONCLUSIONS. This study demonstrates for the first time the potential of HR-MAS ¹H NMR spectroscopy as an analytical tool for use on intact lenses. Near-threshold UVR-B doses led to a generally significant decrease in water-soluble metabolites 1 week after exposure. The lack of dose-dependent changes in the metabolites indicates that repair processes during the first week after UVB irradiation overcome the immediate metabolic disturbances.

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