Aldose reductase messenger RNA in the lens epithelium in vivo: effects of diabetes mellitus and galactosaemia.

1. Quantitative in situ hybridization histochemistry was used to examine the regulation of aldose reductase messenger RNA in the rat lens after the induction of diabetes mellitus or after feeding a 50% (w/w) galactose diet. 2. Although increased staining for aldose reductase in the lens epithelium has previously been observed by immunohistochemistry after 3 weeks of diabetes or after 7 days of galactose feeding, we have not been able to detect any increase in the amount of aldose reductase messenger RNA in these cells as compared with controls (113 +/- 7%, 105 +/- 9%, 100 +/- 7%, respectively) at these time points (P greater than 0.05). 3. After 15 days of galactose feeding, however, there was a significant increase of 140% (+/- 12%) in the amount of aldose reductase messenger RNA in the lens epithelial cells as compared with controls (P = less than 0.001). 4. These results demonstrate that increased availability of galactose, a high-affinity substrate for the enzyme, leads to increased aldose reductase messenger RNA, which suggests a role for aldose reductase in sugar metabolism in the lens.