The Utilization of Hexoses by Excised Rat Tissues

With a modified Warburg, measurements were made on kidney and liver slices and on whole diaphragm muscle of oxygen absorption and of respiratory quotient in Ringer’s-phosphate solutions and in solutions of Ringer’s phosphate to which had been added glucose, fructose or galactose. With kidney and liver both fed rats and animals fasted 24 to 48 hours were used. Galactose was without influence on the respiration of kidney tissue, glucose increased the O2 uptake without changing the R.Q. and fructose caused a greater increase in O2 than did glucose, together with a rise in R.Q. which corresponded exactly to the theoretical rise. Muscle tissue oxidized neither glucose nor fructose and liver tissue was intermediate between the two. It oxidized neither glucose nor galactose but fructose it did burn, to some extent, as indicated by a small increase in the O2 consumption and a rise in R.Q. The latter, however, was so much higher than the theoretical rise as to suggest that processes other than oxidation were taking place, e.g., the conversion of some of the fructose to fat. The possible role of the liver in carbohydrate metabolism is discussed.