Role of renal gluconeogenesis in the maintenance of glycaemia after L-tryptophan administration to rats.

The time-course of liver and kidney gluconeogenesis after L-tryptophan administration has been studied. Two and half hours after injection of L-tryptophan (0.5 g/kg body wt) a 97% inhibition of hepatic gluconeogenesis in starved rats was observed. Twelve hours later, the inhibition remained 35%. Hepatic glycogen was almost completely depleted (97%) in fed rats after 5 hours. At this time there was a severe hypoglycaemia in fed and 48 h starved rats which gradually disappeared with time, the values going back to normal after 12 hours. Tryptophan treatment was associated with a significant increase in renal gluconeogenesis in fed and 48 h starved rats with a maximum at 5 h (165% and 190% respectively). When hepatic gluconeogenesis was constantly inhibited in fed rats by periodic injection (every 4 h) of L-tryptophan, renal gluconeogenic ability remained increased throughout the experiment while blood glucose concentrations did not change. These observations suggest that kidney contributes to maintain glycaemic homeostasis under these conditions of liver gluconeogenesis impairment.