Fig. 7.

Absorptive fluxes of 15 amino acids (AAs) (native concentrations): luminal H⁺ stimulation. Chambered mucosae isolated from cecum (left) and proximal colon (right) were incubated with luminal Parson’s solution (buffered to pH 7.4 with HEPES) containing 15 AAs at their native cecal concentrations. Samples of the serosal bath were collected after 45 min and analyzed by UPLC-MS (green bars). Replicate experiments were carried out in an otherwise identical luminal solution buffered to pH 6.2 with PIPES (lavender bars). The component stimulated by luminal H⁺ is indicated by the orange bars. Values are means ± SE obtained with tissues isolated from the rat cecum (n = 8) and proximal colon (n = 7). *P < 0.05.