Effect of aldose reductase inhibitors on naphthalene cataract formation in the rat

Naphthalene feeding can result in cataract formation in rats and rabbits due to specific metabolites of naphthalene. The concomitant administration of the aldose reductase inhibitor Al1576 to naphthalene-fed rats was proven to prevent cataract formation. To determine whether this effect was directly linked to the ability of Al1576 to inhibit enzyme aldose reductase, a variety of structurally diverse aldose reductase inhibitors, including the carboxylic acids tolrestat, Ponalrestat, and FK366, and the spirohydantoins, sorbinil and Al1576, were investigated for their ability to inhibit naphthalene-induced cataracts. Brown Norway rats, administered naphthalene by gavage, were fed normal rat chow containing these aldose reductase inhibitors at levels known to inhibit sugar cataract formation. The lens changes in these rats were monitored over a 90-day period by portable slit-lamp microscopy and histologic study. Al1576 showed a dose-dependent reduction in naphthalene-induced cataract formation, with no naphthalene-associated deposits seen in toluidine blue-stained lens sections. Sorbinil also reduced lens changes, whereas tolrestat, Ponalrestat, and FK366 had no effect. These results suggest that inhibition of naphthalene-induced cataract formation by structurally diverse aldose reductase inhibitors was not linked to the inhibition of aldose reductase.