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The Effects of Sugars on the Respiratory Exchange of Cats¹

Nutrition Laboratory, Carnegie Institution of Washington, Boston, Massachusetts

The respiratory exchange was measured in successive 1/2-hour periods for 4 hours with five cats in the basal state, after ingestion of 75 ml. of water, after ingestion of 10 gm. of glucose, fructose, galactose, sucrose, maltose, or lactose, and after ingestion of a combination of 5 gm. each of glucose and fructose or of glucose and galactose.

The values of the basal R. Q. were uniform, for the most part, and did not show a marked tendency to change during the eight 1/2-hour periods of measurement. The ingestion of water resulted in a rise in R. Q. with one cat for the entire 4 hours but with the other cats only in the first 1/2-hour period. Glucose caused the greatest rise in R. Q., and the peak occurred in the sixth and seventh 1/2-hour periods. All the other sugars, disaccharides as well as monosaccharides, caused definite rises in the R. Q.

On the assumption that in the control experiments with water only fat and protein were metabolized and that in the experiments with the sugars the protein metabolism of a given cat was the same as its average protein metabolism in the experiments with water, it was calculated that the metabolism of carbohydrates was highest after glucose and lower after galactose and fructose in the order named. The cats were able to metabolize the disaccharides nearly as well as would be expected, in view of their constituent monosaccharides formed by hydrolysis. When combinations of hexoses equivalent to 10 gm. of sucrose or lactose were ingested, the resultant metabolism of carbohydrates was greater than would be expected from the sum of the amounts metabolized after ingestion of the respective hexoses given separately.

Cats resemble men in the metabolism of the monosaccharides in that they show increases in R. Q. and in carbohydrate metabolism after ingestion of these sugars, but they differ from men in that the peak effect does not occur so promptly and, qualitatively, the order of magnitude of the effect is not the same.

Manuscript received 16 June 1944.