Effect of Topical Glucocorticoid Administration on the Protein and Nonprotein Sulfhydryl Groups of the Rabbit Lens

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Abstract
The effects of topical administration of glucocorticoids on rabbit lenses are described. Animals were divided into three groups. The first group (A) served as control, the second (B) and the third (C) group were treated with betamethasone and fluorometholone, respectively. After 40 days of treatment there was a significant fall in the levels of nonprotein sulfhydryl (-SH) groups (group A: 3.82 .+-. 0.21; group B: 2.61 .+-. 0.11; group C: 1.93 .+-. .+-. 0.13 .mu.mol/lens) and protein of -SH groups (group A: 8.215 .+-. 1.023; group B: 4.120 .+-. 0.631; group C: 4.068 .+-. 0.538 .mu.mol/lens). Also ascorbic acid levels showed a significant decrease both in lens and in aqueous humor. No differences were noted in the reduced glutathione content in aqueous humor. The fall in nonprotein and protein -SH could be the first event in the well-known biochemical changes that occur in steroid-induced cataract. The mechanism underlying steroid-induced damage could be due to a conformationl change of lens cyrstallins which results in an unmasking of -SH groups with a consequent increased susceptibility to oxidation. The decrease of ascorbic acid should represent an effect of the fall in the glutathione system. Lastly, it is hypothesized that the protective effect exerted by some substances, such as vitamin E and ascorbic acid, occurs by counteracting this oxidation.