Failure of D-fructose to stimulate protein biosynthesis in pancreatic islets

Rat pancreatic islets were incubated for 90 min with L-[4-3H]phenylalanine in either the absence or presence of D-glucose and D-fructose. Relative to basal value, D-glucose (16.7 mM) increased the incorporation of the tritiated amino acid into trichloroacetic acid-precipitable material. However, when D-fructose was tested in the 80 to 240 mM concentration range, it failed to stimulate islet biosynthetic activity. Since D-fructose causes, in the same concentration range, a dose-related stimulation of insulin release, the dissociation between the biosynthetic and secretory responses to D-fructose supports the view that the insulinotropic action of the ketohexose does not entail the same metabolic determinants as those operative in glucose-stimulated islets.