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.