EFFECT OF ABOMASAL INFUSION OF ALANINE AND ASPARTIC ACID ON GROWTH HORMONE SECRETION IN SHEEP

Effects of animo acids infusion into the abomasum on plasma growth hormone (GH) concentration were investigated using three wethers of 54 kg of average body weight. Wethers were infused with either 3.25 mmol/kg BW/day of sodium chloride solution (control), 3 mmol/kg BW/day of alanine (Ala), or 3 mmol/kg BW/day of aspartic acid (Asp) continuously for five days through an abomasum cathether in a $3{\times}3$ Latin square desing. On the day of starting infusion (day 0) and day 4 blood samples were collected from a jugular vein every fifteen minutes for six hours after feeding, and their GH concentrations were measured. Blood samples were also collected immediately before starting infusion (day 0), and before feeding of day 1, day 2 and day 4, and their plasma free amino acid concentrations were measured. In the animals infused with Ala, plasma free Ala concentration was increased by Ala infusion and it continued for four days. Plasma GH concentration of these animals increased on day 0, but this phenomenon disappeared on day 4. In the animals infused with Asp, the increase in plasma Asp concentration was observed only on day 1. Plasma GH concentration of these animals was not affected by Asp infusion. These results suggest that continuous Ala infusion stimulates GH secretion for a short period, but the effect would not last long, and that continuous Asp infusion does not affect plasma GH concentration.