1. The simultaneous effects of an intravenous glucose infusion on plasma urea, glucose and alanine kinetics were investigated in normal post-absorptive man.
2. The primed constant intravenous infusion of compounds labelled with stable isotopes, [15N2]urea, [6-2H]glucose and [3-13C]alanine, was used.
3. The rate of appearance of glucose and urea in the plasma was rapidly reduced by the 17.7 μUmol min−1 kg−1 glucose infusion.
4. In contrast, during the glucose infusion there was an increased rate of appearance of alanine in the plasma, and an increased percentage of glucose carbon atoms derived from alanine.
5. Reduced production of glucose and urea during the glucose infusion was not due to decreased gluconeogenesis from alanine.