The Effect of Galactose on the Human Respiratory Quotient and Alveolar Carbon Dioxide

Abstract

The respiratory quotient was determined with a human subject in 15-minute periods before and for 3 hours after the ingestion of 250 cc. of water as a control, 25 and 50 gm. each of galactose, 25 gm. of galactose plus 25 gm. of glucose, and 50 gm. of lactose, in 250 cc. of water. Alveolar carbon dioxide was determined simultaneously at 7- to 8-minute intervals during the periods of respiratory exchange. There were five experiments in each group The ingestion of 25 and of 50 gm. of galactose was accompanied by marked drops in the alveolar carbon dioxide that lasted over 1 hour with 25 gm. and over 1¾ hours with 50 gm. of galactose. In the same periods of time there were marked rises in the respiratory quotients. The correlation coefficients between the alveolar carbon dioxide and the respiratory quotients in the two groups averaged -0.640 and -0.666. With 25 gm. of galactose and of glucose together there was a drop in alveolar carbon dioxide and a rise in respiratory quotient, but the changes in the two factors were not synchronous and the correlation coefficients between the two factors averaged only - 0.424 with a P.E._r of ± 0.135. After 50 gm. of lactose there was a fall in the alveolar carbon dioxide for ½ hours, but the maximum respiratory quotient came earlier, in the third quarter-hour, so that the correlation coefficient between the two factors was only -0.235. Evidently there was a latency in the effect on the alveolar air due to the time required for the hydrolysis of the lactose. Although organic acids were not determined in the blood or urine, the falls in alveolar carbon dioxide accompanying the rises in the respiratory quotient after the ingestion of galactose indicate the formation of acid products in the intermediary metabolism of galactose. The ascending order of elimination of reducing substances (sugar) in the urine was: control series, 50 gm. lactose, 25 gm. each of glucose and galactose, 25 gm. of galactose, and 50 gm. of galactose. The increases in the catabolism of carbohydrates and in the heat production in these series agreed in the main with similar series previously carried through in this laboratory.