Lysine and Glycyl-L-Sarcosine Absorption Across Ovine Forestomach Epithelium In Vitro

Abstract

Lysine absorption by ruminal and omasal epithelia was studied using parabiotic chambers that were sampled for 60-min. Lysine appearance in serosal buffers and the accumulation of lysine in tissues increased linearly (P < .001) with time. Lysine appearance in serosal buffers of ruminal tissue increased proportionally as the concentration of lysine increased in mucosal buffers. However, lysine appearance in serosal buffers of omasal tissue increased proportionally to a substrate concentration of 1.5 mM, then plateaued. Total absorption (tissue accumulation plus serosal appearance) increased linearly for ruminal tissue; however, for omasal tissue, total absorption increased linearly to 1.5 mM (P < .001), then plateaued. Using omasal epithelium, glycyl-L-sarcosine (Gly-Sar; .1 mM) absorption was studied during co-incubation with glycine and peptide substrates (each at 5 mM). Accumulation of Gly-Sar in omasal epithelium was greatest (P < .05) when Gly-Sar was present alone. Glycine inhibited (P < .05) Gly-Sar accumulation by 20%, whereas peptide substrates inhibited (P < .05) Gly-Sar accumulation by 60 to 85%. The absorption of Gly-Sar (.1 mM) alone or during co-incubation with either 10 mM butyric acid, or a mixture of VFA was also studied. Accumulation of Gly-Sar in tissue was greatest (P < .05) when Gly-Sar was present alone; butyric acid and VFA inhibited (P < .05) Gly-Sar accumulation by 50 to 84%. These results suggest absorption of amino acids and peptides by the omasum, and also suggest the mechanism involves mediated as well as possibly paracellular transport.