Response of Rats to Diets Containing Propylene Glycol and Glycerol

Abstract

The present paper is a brief preliminary report regarding some of the principal observations in connection with experiments which were started in 1941 in an attempt to compare the physiological effects of propylene glycol and glycerol when fed to rats at different levels of intake. The first series of growth experiments covered a period of 20 weeks. The basal ration consisted, in parts per 100, of casein 20, salt mixture 4, Cell-U-Flour 2, butter fat 6, cod liver oil 2, brewer's yeast 6, and corn starch 60. Each experimental group consisted of 6 to 10 young rats. The basal ration was modified by replacing corn starch with glycerol and propylene glycol, respectively, at levels of 1, 3, 6, 10, 15, 20, 30, 40, 50, and 60 parts per 100 of total ration. Consequently, the first series of experiments comprised 21 dietary groups. In a second series of experiments, groups of young rats were fed 4 basal diets identical with that of the first series with the exception that in 3 of these starch was replaced by glucose, sucrose, or dextrin, respectively. In this series, propylene glycol and glycerol were fed only at a 30% level, replacing, in each case, 30 parts of the carbohydrate. A third series of feeding trials was conducted in which propylene glycol and glycerol were fed in isocaloric amounts at a level approximating 30% of the diet. In the first series of experiments, no marked differences in growth response could be detected until the alcohols were fed at the 30% level. At this level the glycerol-fed animals grew at an approximately normal rate, while the propylene glycol animals grew less rapidly. Young rats, starting at 21 to 28 days of age, lost weight and died in a few days when the diet contained 40, 50, or 60%.