GLYCYL-L-SARCOSINE ABSORPTION ACROSS OVINE OMASAL EPITHELIUM DURING COINCUBATION WITH OTHER PEPTIDE-SUBSTRATES AND VOLATILE FATTY-ACIDS

To define the interactions between the absorption of glycyl-L-sarcosin e (Gly-Sar; .1 mM) and glycine, L-methionylglycine, glycyl-L-leucine, L-carnosine, or L-methionylglycyl-L-methionyl-L-methionine (each at 5 mM), ovine omasal epithelium was collected from eight wethers (average BW = 69 +/- 8.2 kg) and mounted in parabiotic chambers. [1,2]-[C-14]G lycyl-L-sarcosine was used as a marker to monitor the presence of Gly- Sar. The Gly-Sar concentration in the omasal epithelium after 60 min o f incubation was greatest(P < .05;.0055 nmol/mg dry tissue) when only Gly-Sar was present. Glycine inhibited (P < .05) Gly-Sar movement thro ugh the tissue by 20%, and peptide substrates inhibited (P < .05) Gly- Sar movement by 60 to 85%. The appearance of Gly-Sar in serosal buffer s increased quadratically (P < .001) with time. Numerically, Gly-Sar a ppearance in serosal buffers was stimulated by the presence of glycine and peptide substrates. In a second experiment, ovine omasal epitheli um was collected from four lambs (average BW = 47 +/- 6.0 kg) to deter mine the interactions of Gly-Sar absorption (.1 mM) alone or when coin cubated with either 10 mM butyric acid, or with a mixture of VFA (50 m M acetic acid, 40 mM propionic acid, and 10 mM butyric acid). The move ment of Gly-Sar through the omasal epithelium was greatest (P < .05) w hen only Gly-Sar was present, and the VFA mixture inhibited (P < .05) Gly-Sar movement by 84%. Results from these studies support the idea t hat peptides can be absorbed across omasal epithelium and that the pro cess involves mediated as well as nonmediated mechanisms, including po ssibly paracellular transport.