Influence of dietary protein concentrations or of duodenal amino acid infusion on cholecystokinin release in goats

1. 1. Whether dietary protein levels or duodenal infusion of amino acids alters the release of cholecystokinin (CCK) in blood plasma of goats was investigated in three experiments. The CCK determination was done by radioimmunoassay with specific CCK-8 antibody. The male adult Shiba goat, a miniature Japanese native goat, was used. 2. 2. In Experiment 1, four goats were offered a diet containing 4.94 g crude protein (CP)/kg BW^0.75 for the first 7 days. They were then given a diet containing 5.86 g CP/kg BW^0.75 for 7 days and thereafter 6.79 g CP/kg BW^0.75 for the following 7 days. On the last day of each experimental period, blood samples were taken from the jugular vein at zero (before feeding), 30, 60, 120, 240 or 360min after the feeding of the diet. Plasma CCK levels were not affected by dietary protein levels and time after feeding. 3. 3. Influence of phenylalanine or tryptophan (2 mmol/20 ml) infusion into the duodenum was investigated by a 3 × 3 latin square in Experiment 2. Plasma CCK level was determined at 15 min intervals for 1 hr. Both phenylalanine and tryptophan gradually enhanced plasma CCK concentrations with time after infusion. 4. 4. Branched-chain amino acids such as leucine and isoleucine were supplemented intraduodenally in Experiment 3 as in Experiment 2. No significant change in plasma CCK levels was observed.