Effect of tryptophan on the utilization of intra-duodenally infused labelled glucose in piglets given food at 1 center dot 35 times maintenance energy

Two experiments were conducted. The first, studied the chronic effect of tr yptophan (trp) on glucose disposal and the second, the acute effect of trp on glucose disposal. In experiment 1, 12 piglets were allocated either to a try deficient diet (T0) or a trp adequate diet (T1). After 14 days a 240-m in intraduodenal infusion of glucose (130 mu mol/kg per min) associated wit h D-(U-C-14) glucose (1.18 kBq/kg per min) and an intrajugular infusion of D-(6-H-3) glucose (1.85 kBq/kg per min) were started. In experiment 2, 18 p iglets were given a trp adequate dirt (T1) for 14 days. The piglets were th en divided into two groups and received an intraduodenal infusion of either glucose (130 mu mol/kg per min) or glucose plus trp (0.53 mu mol/kg per mi n) for 240 min. At the same time an intrajugular infusion of D-(U-C-14)gluc ose (1.48 kBq/kg per min) and D-(6-H-3)glucose (2.59 kBq/kg per min) ions g iven to all piglets. Blood samples were taken at regular intervals during t he infusions for the measurement of plasma concentrations of insulin, gluco se, lactate and blood specific activities of C-14-glucose, C-14-lactate, H- 3-glucose and H-3-lactate. At the end of the infusion, samples were taken f or the measurement of the accumulation of C-14 and H-3 in glycogen. In expe riment 1, plasma insulin concentrations were higher in the T0 compared with the T1 group (at 30 min respectively, 837.7 (s.e. 56.6) v. 404.9 (s.e. 56. 6) pmol/l, P < 0.001). Glucose concentrations were also higher in T0 compar ed with T1 (at 30 min respectively, 10.9 (s.e. 0.54) a. 9.3 (s.e. 0.54) mmo l/l, P < 0.05). Glucose flux was unaffected by trp in both experiments. The accumulation of labelled glucose into liver and carcass glycogen was not a ffected by trp. The route of administration of glucose label had a signific ant effect on the percentage of label accumulated in liver glycogen. When b oth C-14 and H-3 were infused into the jugular vein there was no difference in the accumulation of the two tracers in liver glycogen (22.7 v. 21.8% of that infused, P > 0.05, respectively). However, when C-14 was infused into the duodenum and H-3 into the jugular vein, accumulation into liver glycog en was higher for C-14 compared with H-3 (19.9 v. 15.6%, P < 0.001, respect ively). In conclusion, trp does not appear to influence glucose disposal me asured at the end of a 240 min intraduodenal glucose infusion. Contrary to results published from experiments with vats the indirect pathway for glyco gen synthesis (glucose --> lactate --> glycogen) does not appear to occur i n underfed piglets.