Fig. 3.

Release of endogenous amino acids (AAs). Ussing chambered rat cecum (top, n = 5) and proximal colon (bottom, n = 6) were preincubated for 20 min in bilateral Parson’s solution lacking AAs and then rinsed thoroughly with fresh solution twice. Samples of the luminal bath and serosal bath were collected over two successive 45-min intervals (0–45 min: blue bars; 45–90 min: orange bars) and analyzed by ultra-performance liquid chromatography-mass spectrometry. Values are presented as rate of AA release (means ± SE) into the luminal bath (left) or into the serosal bath (right).