The Relation of Ingested Carbohydrate to the Type and Amount of Blood and Urine Sugar and to the Incidence of Cataract in Rats1
Helen S. Mitchell,
Oreana A. Merriam and
Gladys M. Cook
Massachusetts State College, Amherst
1. Blood and urine sugar studies have been made on rats fedon adequate rations containing 62 and 70% lactose, 25 and 35%galactose, 35% fructose, 35% xylose and 70% starch.
2. Determinationsof total and nonfermentable sugar were madeon both blood andurine specimens from the various ration groups.
3. Total bloodsugar values were higher on galactose rationsthan on lactosebut above normal in all animals on cataractproducing rations.
4. The nonfermentable fraction of blood sugar was chieflyresponsiblefor the differences in total blood sugar in thevarious groups,the fermentable fraction remaining more nearlyconstant andwithin the range of normal blood glucose.
5.Average total blood sugar values of three strains of ratsfedon 35% galactose ration were strikingly similar, in contrastto the differences observed in susceptibility to cataract amongthe same groups.
6. A fructose-starch ration caused no hyperglycemiaand no eyechanges.
7. A xylose-starch ration brought abouta slight elevation inblood sugar and some early transitorylens changes which didnot progress beyond this stage.
8.Insulin-protamine (Lilly) failed to lower blood galactoseorreduce the speed of cataract development on a 25% galactoseration.
9. A galactosuria of varying degrees was observedin all ratson lactose and galactose rations, relatively moresevere inthe latter and absent in starch-fed control groups.
10. It may be concluded that galactose is the sugar responsiblefor both the high blood and the high urine sugars observed inrats fed on lactose and galactose rations and must be the majoretiological factor in this type of cataract.
1 Published as contribution no. 259 of the Massachusetts AgriculturalExperiment Station.