Specific Activity of Carbon Dioxide expired by Rats after Oral Sucrose and Other Sugars

Abstract

A COMPARISON of the rates at which the respiratory quotient (RQ) rises after various sugars are given by mouth to human beings or dogs suggests that sucrose is more rapidly metabolized than either glucose or fructose, or a mixture of these monosaccharides^1–4. Nevertheless, the interpretation of the RQ is not unequivocal. In a more direct investigation of the rates at which oral sucrose, glucose and fructose and certain other sugars are metabolized, sugars labelled with radioactive carbon were fed to rats and the comparative rates at which radioactive carbon dioxide was expired were determined. The radioactive sugars were obtained from the Radiochemical Centre, Amersham, except labelled maltotriose, which was prepared by one of us (A. F. M. M.) by hydrolysing radioactive starch and separating by charcoal adsorption and chromatography on paper.