Fig. 4.

Absorptive fluxes of amino acids (AAs) (0.5 mM) by jejunum, cecum, and proximal colon. Chambered mucosae isolated from the jejunum (brown bars), cecum (blue bars), and proximal colon (red bars) were preincubated for 20 min with luminal Parson’s solution containing 11 nonessential AAs (as designated on left) or 9 essential AAs (as designated on right). After rinsing the chambers with fresh solution, samples of the serosal bath were collected after 45 min and analyzed for the indicated AAs by ¹H-NMR. Absorptive flux is defined as the rate of serosal AA accumulation minus basal serosal AA release. Basal AA release from the jejunum was not measured directly and was assumed to equal that from the cecum. Values are means ± SE; n = 3–5.