For the first time, the effects of single and repeated UVR doses on the metabolic profile of the rabbit cornea were analysed and compared. The combination of HR-MAS 1H NMR spectroscopy and modern statistical methods (multivariate analysis, one-way ANOVA) proved suitable to assess the overall view of the metabolic alterations in the rabbit corneal tissue following UVB radiation exposure.

Selenite-overdose cataract is an extremely rapid and convenient model of nuclear cataracts in rats. It was first properly described by Ostada´lovaé t al. (1978). Similarly to ultraviolet (UV)-induced cataract, the biological balance of lens is supposed to be disturbed by oxidative stress, but surprisingly, the effect on the metabolic profile of the lens seems to be considerably different. Nowadays, UV-induced cataract is among the most widely studied cataract models and an explanation of different metabolic responses to oxidative stress in selenite-overdose cataract might help us understand the mechanisms of other cataract types. The formation of selenite-induced nuclear cataract is hypothesized to be a result of glutathione (GSH) loss from the lens. Thereafter, the capacity of GSH to buffer the oxidation ⁄ reduction status of lens metabolism is diminished, and the sensitivity of rat lenses to oxidative stress is enhanced (Mitton et al. 1997). The metabolic pathways of GSH depletion are not fully understood, and therefore further studies must be performed to clarify this process.As a consequence of selenite treatment, the metabolic profile of the rat lens is dramatically changed. Between 24 and 96 hours after selenite injection, the total pool of free amino acids (excluding taurine) is elevated and remains increased for 8 days (Mitton et al. 1997 ABSTRACT.Purpose: To correlate certain levels of lens opacification with high-resolution magic-angle spinning proton nuclear magnetic resonance (HR-MAS 1 H NMR) spectroscopy analysis of the biochemical changes in rat lenses in a selenite cataract model. Methods: Selenite cataract was induced by injecting 13-day-old Sprague-Dawley rat pups with a single subcutaneous dose of sodium selenite (3.28 mg ⁄ kg in 0.9% sodium chloride solution). Lens opacification was observed using a photographic slit-lamp microscope at selected time-points 3, 6 and 9 days after selenite injection and was then graded (levels 0, 1 and 2). The animals were killed after the slit-lamp microscopy, lenses were removed and HR-MAS 1 H NMR spectra from intact lenses were obtained. Relative changes in metabolite concentrations were determined after comparison with matched lenses from untreated animals. Results: Photographic slit-lamp microscopy revealed different stages of cataract in all animals treated with selenite. In the high quality HR-MAS 1 H NMR spectra of the lenses, more than 30 different metabolites were identified in each lens. With the exception of taurine, the concentrations of all amino acids showed a significant increase (p < 0.05) in the second level of cataract. By contrast, glutathione (GSH), succinate and phosphocholine concentrations were significantly reduced. Conclusions: For the first time, this study demonstrates the potential to correlate the level of lens opacification with the biochemical changes obtained with HR-MAS 1 H NMR spectroscopy analysis in a selenite cataract model.

Application of a Carr-Purcell-Meiboom-Gill spin echo pulse sequence was found to have a great advantage for correct analysis of the results obtained with NMR spectroscopy of aqueous humour from eyes where increase of protein level due to an inflammatory process could not be excluded.

HR-MAS 1H NMR spectroscopy showed its suitability to assess the natural alterations in the metabolic profile of maturing rat lens. The results can be used in future cataract research designed to evaluate the metabolic effect of different cataractogenic agents during this postnatal period.

This study reveals the cumulative effect of repeated UVB irradiations, and shows that even a 48-hour interval between subsequent UVR-B exposures is not sufficient for the healing processes to restore lenticular integrity.