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 >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 = < 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.