Enhanced release of cholecystokinin in chickens fed diets high in phenylalanine or tyrosine.

1. Whether the ingestion of excess phenylalanine (Phe) or tyrosine (Tyr) in diets alters the release of cholecystokinin (CCK) into the blood was investigated in chickens. A single meal of control, Phe excess, or Tyr excess diets was given through a stomach tube, followed by the CCK determination with specific CCK-8 antibody. 2. Plasma CCK level increased significantly at 30 min after feeding the diets: about 2.5 times the basal level in the control group and about 3 times the basal level in both of the experimental groups. 3. The Phe excess diet significantly delayed crop emptying rates compared to the control diet, while the Tyr diet on the contrary enhanced the emptying rate. 4. Enhanced plasma CCK levels and delayed crop emptying by Phe excess diet are suggested to be associated with depressed food intake.