Metabolic changes in rabbit lens induced by treatment with dexamethasone

Metabolic changes in the rabbit lens have been studied by means of nuclear magnetic resonance spectroscopy. These changes have been induced by prolonged topical treatment with dexamethasone. Our results demonstrate an increase in sorbitol, sorbitol-3-phosphate, fructose-3-phosphate, glycerol-3-phosphate and glucose-6-phosphate levels and a decrease in glutathione sulphate (GSH) and myo-inositol levels, in agreement with what was observed in lenses from streptozocin-diabetic rats before lens opacity. The hyperglycaemia can only partially explain all these observed biochemical variations. The lack of increase in the intermediates of pentose cycle, such as sedoheptulose-7-phosphate, seems to support the hypothesis of an inhibition of glucose-6-phosphate dehydrogenase by dexamethasone treatment. Finally dexamethasone treatment induces a decrease in GSH. The decreasing or the loss of GSH has been suggested as a possible pathogenic mechanism in the cataract formation.