Reduced and oxidized glutathione concentrations in the lenses of riboflavin-deficient rats.

The lens, in particular the lens epithelium, contains an uncommonly high concentration of reduced glutathione (GSH). It has been implicated to play a significant role in the maintenance of a reduced atmosphere in the lens. A diminution in the content of GSH has been observed during the formation of several forms of cataracts in experimental animals and in human subjects (1, 2). Glutathione reductase reduces oxidized glutathione (GSSG) back to GSH, and mediates the release of GSH from protein glutathione mixed disulphides. In cataractous lenses, this enzyme activity is decreased. Riboflavin, which is a precursor of flavin adenine dinucleotide (FAD), is a necessary coenzyme of glutathione reductase. Some studies (3-5) have suggested a riboflavin deficiency as a cause of cata ract formation, while another (6) has disputed the association. In the present study, the changes in the content of glutathione, GSH and GSSG, and in glutathione reductase activity in the lenses of B2-deficient rats were investigated. Wistar-strain male rats weighing about 50-70g were used. The rats were fed on a riboflavin-deficient diet (Oriental Yeast Co., Japan) as reported previously (4). Experiments were carried out 4 weeks after the start of administration of the B2 deficient diet. NADPH-cytochrome c reductase activity, glutathione reductase activity and B2 content of liver were determined as a marker of B2-deficient status. NADPH-cytochrome c reductase activity, glutathione reductase activity and B2 content of liver of the normal group were 0.112•}0.011ƒÊmol/min/mg microsomal protein, 48.1•}1.8 units/mg 9,000•~g sup. protein and 37.0•}1.9ƒÊg/g liver re spectively, whereas those of the B2-deficient group were (same units) 0.069•}0.010, 28.2•}2.3 and 21.0•}2.1, respectively. A significant difference was found in the