ABSORPTION OF L-CARNOSINE, L-METHIONINE, AND L-METHIONYLGLYCINE BY ISOLATED SHEEP RUMINAL AND OMASAL EPITHELIAL TISSUE

The absorption of carnosine, methionine, and methionylglycine (using S -35-methionine and S-35-methionylglycine as representative markers) ac ross ruminal and omasal epithelia collected from four (carnosine) and seven sheep (methionine and methionylglycine) were studied using parab iotic chambers that were repeatedly sampled over 240-min incubation. T he quantity of all substrates transferred was linearly (P <.01) depend ent; on initial substrate concentration and time. More (P < .01) carno sine, methionine, and methionylglycine was transferred across omasal t han across ruminal epithelia. Carnosine was absorbed across both tissu es without hydrolysis. Methionylglycine was transferred intact across both tissues. A greater (P <.01) quantity was hydrolyzed by omasal tha n by ruminal epithelia, after 240 min of incubation. Greater (P < .06) quantities of methionine and methionylglycine accumulated in ruminal tissue after 240 min. Total absorption of methionine and methionylglyc ine did not differ within tissues, but total absorption of both substr ates was greater (P <.01) by omasal tissues. There was little evidence for saturable absorption. These results indicate that omasal epitheli al tissue possesses a greater ability to absorb both free and peptide- bound amino acids than does ruminal epithelial tissues.