Studies on the transportin vitroof lysine, histidine, arginine and ammonia across the mucosa of the equine colon

Abstract

Summary Discs of stripped mucosa from the proximal ventral colon were prepared immediately after slaughter of 8 Shetland cross‐breed ponies. The mucosae were fixed in incubation chambers and used in incubation experiments to study the transmucosal fluxes of the amino acids lysine, histidine and arginine (150 min) and of ammonia (90 min). When the amino acid concentrations in the mucosal solution were in the physiological range (2.8–3.0 mmol/l) no transport to the serosal side of the tissue was found. When the concentrations were raised 10‐fold, less than 2% of the mucosal amino acid pool was recovered in the serosal solution. Ammonia was transported across the mucosa at significant rates although only 63% of the ammonia that disappeared from the mucosal solution was found in the serosal solution. The findings show that the equine proximal colon is virtually impermeable to luminal free amino acids whereas ammonia is transported at rates equal to, or higher than those observed with rumen mucosa from sheep.

Characterization of L-lysine transport across equine and porcine jejunal and colonic brush border membrane

“…Studies of L-Lys uptake by the equine large intestine using both in vivo and in vitro methods have yielded contradictory results (Slade et al, 1971;Bochröder et al, 1994). Our results support those of Slade et al (1971), who demonstrated appearance of labeled Lys and other essential AA in the cecal vein after cecal in-fusion of '"'N-labeled microbes in a pony.…”

“…Therefore, it is possible that b""''AT is responsible for L-Lys uptake from the intestinal lumen in both the jejunum and colon of the horse. On the other hand, transmucosal potential difference of L-Lys, L-His, and L-Arg measured across proximal colonie discs was low, indicating minimal transport of these AA (Bochröder et al, 1994). Also, Freeman et al (1989) Wnd no transport of L-Ala determined with transmucosal potential difference across cecal mucosa harvested from horses.…”

“…Also, Freeman et al (1989) Wnd no transport of L-Ala determined with transmucosal potential difference across cecal mucosa harvested from horses. Bochröder et al (1994) and Freeman et al (1989) used mucosal sheets; hence, they characterized transport across both the BBM and the basolateral membrane. In our study, transport was characterized across the BBM only.…”

Nitrogen compounds and volatile fatty acids absorption from the caecum and colon of sheep

“…Bochroder et al (1994) reported that the colon epithelium of the horse is not permeable for histidine, lysine and arginine. Schmitz et al (1991) found arginine absorption from the caecum of cow, pig and horse below 10%.…”

“…There is evidence that substantial quantités of microbial and feed protein are digested in the large intestine and that nitrogen is absorbed predominantly in the form of ammonia (Zebrowska, 1975;Dixon and Nolan, 1982;Schmitz et al, 1991;Bochroder et al, 1994). Some reports show that amino acids can be absorbed from the caecum of pigs and mice (Robinson et al, 1973;Olszewski, 1975;James and Smith, 1976;Jarvis et all., 1977), but data is lacking on the absorption of amino acids from the large intestine of sheep.…”