TRANSPORT OF L-VALINE BY THE CHICKEN CECUM

1. We have studied L-valine transport by the caecal segments of 6- to 8-week-old chickens. Isolated enterocytes from the proximal caecum inc ubated with 0.1 mM L-valine can accumulate the substrate against a con centration gradient. After 50 min incubation, the intracellular L-vali ne concentration reached 0.53 mM, a value higher than that observed in enterocytes from the jejunum (0.34 mM; P < 0.01). 2. Enterocytes from the medial and distal caecal regions are unable to transport L-valine uphill (cell concentration: 0.1 mM). 3. Amino acid accumulation by pr oximal caecal cells was Na+-dependent and was inhibited by ouabain and 2,4-dinitrophenol. L-methionine inhibits L-valine uptake and a 2.5 mM concentration abolishes the capacity of enterocytes to accumulate the substrate. 4. The high accumulation ratios shown by the proximal caec um for L-valine suggest a role for this intestinal segment in the abso rption of neutral amino acids present in the caecal chamber.