Abstract
The lens is subject to oxidative damage by photosensitizers, and light. Riboflavin or rose bengal photosensitzed damage to carrier mediated transport systems was studied in cultured rat lenses. Photo-oxidation reduced accumulation of 86Rb, [3H]choline, and [3H]α-aminoisobutyric acid (AIB) in the lens water. The earliest effect was decreased choline accumulation. This was followed by decreased uptake of AIB and 86Rb, and finally by increased 86Rb leakout and loss of clarity. Damage to lens transport by riboflavin or rose bengal was dependent upon light, and air. Superoxide dismutase (SOD) did not block the photo-oxidation by either photosensitizer, indicating that the, superoxide, free radical was not directly responsible for the lens damage. Catalase blocked the effects of riboflavin but not of rose bengal. In contrast, ascorbate blocked the effects of rose bengal but only partially blocked the effects of riboflavin. Therefore it appears that riboflavin acts through a hydrogen peroxide intermediate whereas rose bengal acts through some other intermediate, possibly singlet oxygen.
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