Effects of infusions of lysine, leucine and ammonium chloride into the hepatic portal vein of chickens on voluntary food intake.

1. Adolescent cockerels of a laying strain were prepared with catheters whose tip lay in the hepatic portal vein, to study the effect of 3-h infusions of nutrients on food intake. 2. Lysine, infused into the hepatic portal vein at rates of 150-450 mg/3 h reduced 3-h food intake by up to 58%, for a period of 6 h in previously starved birds, but had no effect on birds allowed free access to food. Infusions made into the jugular vein had no effect, suggesting a role for the liver in monitoring lysine levels. 3. Portal infusion of leucine had a delayed effect while ammonium chloride, infused at isosmolar rates to those of the lysine infusions, had very little effect on intake. 4. The results support the concept of liver sensitivity to amino acids, but the mode of action is not clear; it appears not to be via the effects of ammonia.