Management of aldose reductase mRNA abundance in rat lens undergoing reversal of galactose induced cataracts. A model for gene response to changes in the environment.

Aldose reductase (AR) mRNA concentration in rat lens was quantitated by hybridization of a RNA transcript from a previously described AR cDNA clone to mRNA found in epithelial and cortical cytosols. This was done on normal rat lens and on lens initially made cataractous by feeding of a diet of Purina Chow containing 50% galactose, followed by reversal of the cataracts due to the removal of the galactose from the diet. Recent data from this laboratory has shown that AR mRNA was increased in lens epithelial cells upon administration of galactose; while in the cortex it was reduced to insignificant levels when fiber cell damage became extensive by day 20 on galactose. Present data reveals that, upon removal of galactose from the diet, the lens epithelial AR mRNA was gradually reduced from the high levels found at day 20 of galactose feeding to low levels by day 30 of reversal. On the other hand, the cortex exhibited an initial sudden increase in AR mRNA at days 1 to 6 of reversal and by day 30 it was reduced to levels below those found in the untreated lens. DNA content in the epithelium also began to decrease to normal levels by day 16 following reversal of the cataracts. The data demonstrate that the concentration of AR mRNA in lens of reversed cataracts appears to faithfully reflect the loss of epithelial cellular need for AR mRNA in favor of enhanced differentiation of epithelial cells to secondary fiber cells.