Influence of Protein or Gystine Intake on Cataract-producing Action of Galactose. ∗ †

Abstract

Ever since it was first demonstrated that galactose causes lens changes in rats 1 experiments have been under way in an effort to explain the metabolic disturbances involved. The basal ration of 15% protein, 70% carbohydrate (galactose and starch), 11% fat (including 2% cod liver oil), 4% salt mixture (Osborne and Mendel), and 0.5 gm. dry yeast 3 times a week, has been modified and supplemented in various ways. The following mineral and vitamin modifications have failed to alter the incidence or speed of cataract development; an excess or omission of salt mixture, drastic shifts in the acid-base balance of the ration, excess or lack of vitamins B and G, crystalline ascorbic acid administered orally or parenterally, massive doses of viosterol. Modifications in the types and amounts of fat or carbohydrate (other than galactose or lactose) have also given negative results. An increase in the amount of protein (15% to 30%) from 3 different sources (casein, lactalbumin, and beef muscle, respectively) also failed to alter the rate of cataract development.

A reduction of the protein (casein), however, in a 25% galactose ration, from the regular 15% level to 5% level shortened the time of cataract development from 26.3 to 15 days on the average, a difference which is strikingly significant. Furthermore, growth of rats on the low protein ration was limited, as would be expected, and the lower food intake in this group meant less galactose actually consumed, which fact tends to make the aggravating effect of the low protein still more striking. It is worth noting that an increase of galactose in the basal ration from 25% to 35% is less effective in shortening the time of cataract development than is the lowering of the protein from 15% to 5%.