Aldose reductase (AR) mRNA levels increase when dog lens epithelial cells are exposed to hypertonic conditions. Hybridization of mRNA to an AR cDNA, using Northern and slot blots, showed that AR mRNA is elevated at least fourfold when primary dog lens epithelial cells are grown in media (300 mosmol kg−1) supplemented with 150 m m NaCl (600 mosmol kg−1 final). A time course showed an increase in AR mRNA of approximately twofold by 24 hr with a maximum increase of between four- and eightfold by 48 hr. AR mRNA remained elevated for the duration of the experiment, 8 days. The addition of Tolrestat, an inhibitor of aldose reductase, had no effect on the increased level of AR mRNA in these hypertonically stressed cells. Cells grown in media supplemented with 250 m m sorbitol also showed a substantial increase in AR mRNA. These data indicate, as in other cell types, the lens, a target tissue of diabetes, responds to hyperosmotic stress with an induction of AR expression and suggests that AR may play a role in intracellular osmotic regulation.
