Sorbitol dehydrogenase (SORD) was quantitatively assayed in a family in which four out of five brothers and their father had bilateral cataracts. Three sibs (two of them with cataracts) and both their father and paternal grandfather had SORD activity of about 25% of the reference values; of the other two affected sibs one had about 50% and the other had 75%; the mother and two paternal uncles had about 75%. These results do not define a clear cataract-SORD deficiency etiopathogenic relationship, nevertheless, they strongly suggest activity polymorphism in human red cell SORD, which would be highly relevant not only to the study of cataracts but of other major complications in diabetes.
A boy aged 2 years 8 months presenting the Rubinstein-Taybi Syndrome (RTS) and a history of recurrent gastrointestinal and respiratory infections was studied. Partial deficient cell immunity and intermittent hyperaminoacidemia and aminoaciduria were ascertained. These findings were interpreted as evidence of phenotypic and probably genetic heterogeneity of RTS.
SUMMARY A new fluorimetric method for the quantification of red blood cell (RBC) sorbitol dehydrogenase is described. It is based on the oxidation of sorbitol to fructose, in presence of NAD+, catalysed by the RBC-sorbitol dehydrogenase. The quantity of NADH formed is then measured in a filter fluorimeter. Comparison with an indirect spectrophotometric assay yielded good correlation; however, the present method offers several advantages: it is more rapid, simple and inexpensive. It should be useful to screen for sorbitol dehydrogenase deficiency in large numbers of individuals, particularly patients with diabetes or cataracts.
Summary.Screening for red blood cell sorbitol dehydrogenase deficiency in 12 different mammalian species was performed. A wide inter-species variability in red cell sorbitol dehydrogenase with a virtually complete deficiency in pigs was observed. Aldose reductase and sorbitol dehydrogenase activities in 12 different pig tissues also were measured. Aldose reductase activity was present in all the tissues studied, whereas organ specificity for sorbitol dehydrogenase was observed.Sorbitol dehydrogenase activity was not detectable in lenses, among other tissues, making the pig a potential model for studies in experimental diabetes, particularly for the investigation of sorbitol dehydrogenase deficiency as a risk factor in the development of cataracts.Key words: Aldose reductase, animal models, cataracts, diabetes, red blood cells, sorbitol dehydrogenase.Sorbitol and galactitol are involved in the pathogenesis of diabetic and galactosemic cataracts in man and experimental animals [1]. Theoretically, a sorbitol dehydrogenase (SORD) deficiency could lead to sorbitol accumulation in lenses, among other tissues, and eventually to cataracts. Recently, we investigated this assumption in the population at risk and found a family with congenital cataracts and red blood cell SORD deficiency [2]. Although our results did not define a clear cataract-SORD deficient aetiopathogenic relationship, they strongly suggest activity polymorphism in red blood cell SORD. The role that SORD deficiency may play in the development of diabetic complications could be studied in an animal model with low levels of this enzyme. Red blood cell SORD activity in several mammals has been demonstrated previously [3].The aim of this study was to screen for red blood cell SORD deficiency in animals. These results, as well as those for aldose reductase (AR) and SORD activities in several pig tissues, are presented. Materials and methods Animal materialBlood was drawn and collected in heparin from more than 10 mature animals from each of 12 species: 15 Syrian hamster; 20 balc/C mice; 29 Fort Detrick Dunkin Hartley strain guinea pigs; 20 Sprague-Dawley rats; 17 beagle dogs; 20 New Zealand rabbits; 22 Merino sheep; 10 cattle (Cebu); 10 cattle (Holstein); 20 donkeys; 20 pigs; 19 goats; and 10 horses, all four species mixed breed. Pig tissues were obtained from the slaughter house within 60 rain of butchering and stored at --20 ~ MethodsHomogenates of tissues were prepared according to the method of Op't Hof [4]. The SORD activity in the haemolysates from all the animals was assayed in duplicate by the fluorometric method of Vaca et al. [5] and in pig tissues by the spectrophotometric method of King and Mann [6]. AR was assayed in pig tissues, and in red blood cells of five members of each studied species and five human adults by the spectrophotometric method of Hayman and Kinoshita [7] using DLglyceraldehyde as substrate. Protein determinations were performed according to the method of Lowry et al [8].
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