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We reported that in utero galactose-induced cataracts could be inhibited if aldose reductase inhibitors (ARIs) were included in the galactose diet of pregnant rats. These studies involved morphological and cytochemical approaches. We undertook this investigation to evaluate the effects of ARIs in preventing the formation, accumulation and depletion of dulcitol in lenses of in utero galactose exposed neonates and in mothers during and following pregnancy. Sprague Dawley rats were fed Purina Rat Chow with 50% galactose either with or without 15mg Sorbinil or 1mg Eisai compound E-0722/day/Kg body weight during and following pregnancy. The lenses of neonates and mothers were processed to determine dulcitol concentrations. At parturition there was a significant amount of dulcitol in the lenses of pups and their mothers, which reduced rapidly in the lenses of pups regardless of the diet fed to the nursing mother. While galactose had a cross-placental but not a milk-mediated effect, the ARIs had both cross-placental and milk-mediated effects on dulcitol accumulation and depletion, respectively. The galactose feeding of mothers post-parturition maintained the high lenticular dulcitol concentration and the absence of galactose led to a reduction in lenticular dulcitol. The correlation between dulcitol accumulation and cataract development is discussed.

We have shown that galactose cataract development is delayed or inhibited with the administration of aldose reductase inhibitors (ARIs). Dulcitol forms and accumulates in the lens of rats fed galactose. We undertook investigations to study the effectiveness of ARIs in preventing the formation and accumulation of dulcitol in the lens. Young Sprague Dawley rats were fed Purina Rat Chow with 50% galactose either with or without 15 mg sorbinil, 0.15, 0.5, or 1.0 mg E-0722/day/Kg body weight. At desired intervals following the initiation of diets, the lenses were processed for the determination of galactose and dulcitol levels. The lenticular dulcitol increased significantly in all animals fed galactose reaching a maximum level by approximately 15 days with comparatively lower levels in the groups fed ARIs with galactose; this increase was dose dependent in the groups fed E-0722. There was a subsequent, rapid drop in lenticular dulcitol by 18 days in all dietary groups. Interestingly, a second peak of increased lenticular dulcitol was observed in all groups. The correlation between dulcitol accumulation and cataract development is discussed.

Our previously reported investigations showed that cataracts could be induced in fetal lenses through the maternal feeding of galactose during pregnancy. We also reported that the lens opacity present at birth reverses completely by 30 days of age if there is no further post-natal exposure to galactose. This investigation was designed to investigate if an aldose reductase inhibitor (ARI) has any cross-placental effect in preventing galactose-induced cataracts in fetuses. We have also evaluated if there are any milk-mediated effects of galactose on cataract induction and of galactose and ARI on the maintenance or reversal of opacities induced in utero. Pregnant Sprague-Dawley rats were fed either 50% galactose or rat chow with or without the ARI, (2R,4S)-6-fluoro-2-methyl spirochroman-4,4'-imidazolidine-2',5'-dione (Eisai compound E-0722). Following parturition, pups of mothers from the different dietary groups were either fed by their own mothers or foster fed by lactating females fed either rat chow or 50% galactose with or without the ARI. Lenses of the pups were examined at desired intervals with light and scanning electron microscopes. We observed that: (a) both galactose and the ARI had a cross-placental effect on the fetal lenses in the development and inhibition of cataracts, respectively; (b) galactose had very little, if any, milk-mediated effect on either the induction of cataracts in newborn pups that were born with transparent lenses or the maintenance of cataracts induced in utero; (c) the ARI appeared to have a milk-mediated effect, which accelerates the reversal of cataract associated alterations in lenses of pups with cataracts induced in utero, leading to further reinstatement of lens transparency; and (d) the presence of ARI in the diet of rats during pregnancy and/or post-parturition provided continued protection to the lenses of pups that were exposed to a galactose diet following birth.

Previous cytochemical and biochemical studies have shown an increase in the activity of acid phosphatase and arylsulfatase during the induction of galactose cataracts in rat lenses. It was postulated that these enzymes may be involved in lens fiber degradation observed during cataractogenesis, however, the role of these enzymes in the repair process was not ruled out. The present investigation has evaluated the level of acid phosphatase activity in lenses in which the induction of opacity is inhibited with the aldose reductase inhibitor sorbinil and during the recovery of galactose induced opacity. Sprague-Dawley rats received 50% galactose diet, or galactose diet with sorbinil, or laboratory chow diet. Following 20 days on this diet all rats received lab chow plus 50 mg kg-1 sorbinil (recovery diet). The lenses were removed at desired intervals following the initiation of the above three diets and following the transfer of animals to the recovery diet. Cytochemical localization and biochemical quantitation of acid phosphatase activity were performed with methods previously reported. Most of the enzyme activity was localized within the epithelial cells and superficial cortical fibers. In the epithelial cell layer, the enzyme activity was primarily localized in lysosomes and at extracellular sites near the epithelial cell membrane which abut each other and cortical fibers. In cortical fibers the enzyme activity was observed at various extracellular sites between the cell membranes of neighboring fibers. The effect of sorbinil, if any, and the possible role of acid hydrolases in the repair process during cataract reversal is discussed.

Lens ultrastructure and Na- K-ATPase activity in the lenses of rats fed galactose and a galactose + sorbinil diet (aldose reductase inhibitor) were studied. Lenses of rats on the galactose diet exhibited development of peripheral opacity within 3-4 days. This opacity progressed with the continuation of the galactose feeding, and by 20 days mature cataracts were observed in these animals. The formation of vacuoles, cysts, membrane disruption in the epithelium and fibers, and swelling of fibers accompanied the development of opacity. With the progression of opacity there was a considerable drop in lens Na- K-ATPase activity in the galactose-fed animals. However, the lenses of rats that were treated with sorbinil did not show any of the alterations in the ultrastructure of the epithelium and fibers that accompany galactose cataractogenesis. The level of Na-K-ATPase activity in the sorbinil-treated animals was similar to that found in lenses from the laboratory chow-fed group of rats. These observations further substantiate the role of aldose reductase in sugar-cataract development.

We have demonstrated an increase in activity of arylsulfatase A and B during galactose induced cataract development in rats. Our recent investigation shows that acid phosphatase activity, which increases substantially during galactose cataract development in rats, could be contained to near normal level if Sorbinil, an aldose reductase inhibitor, was fed along with galactose to the rat. We have observed that the activity of other lysosomal enzymes, arylsulfatase A and/or B, also increases during galactose cataractogenesis. In the present report, we provide information with regards to the effect of Sorbinil on the activity of these enzymes during cataractogenesis. A modified Hopsu-Havu and Helminen method (1974) with p-nitrocatecholsulfate as substrate was used for localization of both arylsulfatase A and B; and the method of Hara et al. (1979) was utilized to obtain quantitative data on the level of arylsulfatase A and B activity. Ultrastructural cytochemistry shows that arylsulfatase activity in all lenses was primarily localized in epithelial cells in lysosomes with very little or no activity in cortical fibers. The number of arylsulfatase positive lysosomes and the activity level of these enzymes increased with the progression of cataract development. Galactose induced damage to lens morphology and increase in activity of arylsulfatase A and B was inhibited by inclusion of 50mg/Kg (diet) Sorbinil in the galactose containing cataractogenic diet. However, Sorbinil had no significant effect on the enzyme activity following the establishment of mature cataracts.

Our recent investigations have shown that the Eisai compound, E-0722, (2R-4S-6-fluoro-1-2-methylspirochroman 4,4'-imidazolidine 2,5'-dione) is a more potent aldose reductase inhibitor than Sorbinil (D-6-fluorospirochroman 4,4'-imidazolidine 2,5'-dione). In the previous studies these aldose reductase inhibitors were added to the 50% galactose diet fed to rats to determine their effect on galactose-induced alterations in the lens and the development of cataract. In this report we present our results on the effect of prefeeding the aldose reductase inhibitor, E-0722, on the alterations in rat lens following subsequent feeding of galactose. For this study, young Sprague Dawley rats were prefed either rat chow or rat chow plus 50% galactose containing 1mg/day/Kg body weight of E-0722 for 1 or 2 weeks. After this dietary regimen, the animals were transferred to diets containing 50% galactose for different periods. For controls, rats were fed either rat chow or 50% galactose without the prefeeding of E-0722. Our results obtained through gross observation of the lenses, light microscopic studies of lens sections and assay of Na+-K+-ATPase (NPPase) activity show that the prefeeding of E-0722 prior to galactose feeding delays galactose-induced alterations and the development of mature cataract.