RESPONSES OF GROWTH-HORMONE AND INSULIN TO INTRADUODENAL INFUSION OF 6 AMINO-ACIDS IN CALVES

The responses of growth hormone (GH) and insulin to intraduodenal infu sion of six amino acids were investigated in Holstein-Japanese Black c ross-bred calves. The amino acids used far the intraduodenal infusions were 5 mM per kg body weight of L-arginine (Arg), L-ornithine (Orn), L-glutamic acid (Glu), L-aspartic acid (Asp), L-leucine (Leu) and L-ph enylalanine (Phe). One litre of the Arg, Orn, Glu and Asp solutions (p H5.2) were infused into the duodenum far 90 min. Two litres of Leu and Phe solutions (pH 2.2) were also infused for 90 min. One litre of sal ine (pH 5.2) and two litres of saline (pH 2.2) were infused for 90 min for the control infusions (control 1 and control 2, respectively). Pl asma concentrations of free amino acids were measured at 60 min interv als during the period immediately before to 180 min after the commence ment of the infusions. Plasma concentrations of GH, insulin and glucos e were measured at 20 min intervals during the period 40 min before to 180 min after the commencement of the infusions. The Orn, Leu and Phe infusions markedly elevated (p < 0.05) the plasma concentrations of O rn, Leu and Phe, respectively, but the Arg infusion did not increase t he plasma Arg level. The plasma concentration of glucose decreased aft er the Leu infusion. The area under the curve (AUC) of GH after the co mmencement of the Leu and Phe infusions were larger (p < 0.05) than th e AUC of control 1 and control 2. The AUC of insulin during the Orn in fusion was larger (p < 0.05) than the AUC of control 1. These results indicate that the infusion of some amino acids into the duodenum stimu late the secretion of GH and insulin in calves.