Effect of uridine on cellular UTP and glycogen synthesis in skeletal muscle: stimulation of UTP formation by insulin.

The relation between cellular uracil nucleotides and ability to synthesize glycogen was studied in rat diaphragm incubated in vitro. In the absence of exogenous uridine the tissue content of UTP and rate of glycogen synthesis decreased with time. Uridine added to the medium increased cellular UTP and UDPG and stimulated glycogen synthesis. Insulin significantly increased the synthesis of UTP from extracellular uridine. This action of insulin appeared to be due to a stimulation of phosphorylation of the nucleoside and not to an effect on transport at the concentrations of uridine studied. However, an effect of insulin on transport of uridine at low concentrations cannot be excluded.