Pathways of fructose conversion to glucose and glycogen in liver

[1-14C]fructose and [6-14C]fructose were incubated with liver slices and injected intraportally into rats. Distributions of 14C in the carbons of glucose, the glucose of glucose-6-P, and the glucose unit of glycogen from the slices and from the livers of the rats were determined. With both [1-14C]fructose and [6-14C]fructose the distribution of 14C in the glucose unit of glycogen was the same as in glucose-6-P, in accord with glucose-6-P being an obligate intermediate in the conversion of fructose to glycogen. With [6-14C]fructose the distribution in glucose was also similar to that of glucose-6-P, in accord with a metabolism involving glucose-6-P. With [1-14C]fructose there was a difference in distribution between glucose and glucose-6-P, but the difference was less than the difference reported by Muntz (1) and its significance is not certain. Except for these results with [1-14C]fructose, the data are not in accord with the existence of a pathway for the conversion of fructose to glucose without glucose-6-P as intermediate.