Lysine transport across rat jejunum: distribution between the transcellular and the paracellular routes.

Abstract

SUMMARYTransport of lysine across the rat jejunum has been studied measuring transmural fluxes, Jms and Jam, under short-circuit conditions, influx across the brush-border membrane, Jmc, under open-circuit and voltage-clamp conditions, and steady-state uptake by the isolated mucosa.1. Jly can be described as the sum of a saturable process with a Kt of 3 mm and a Jmax of 2.25 ,umole/cm2 . hr and a diffusional component corresponding to a lysine permeability of 0-014 cm/hr. Also Jlys is well described as the sum of a saturable process and a diffusional contribution described by the same permeability as for 3. The passage of an electrical current across the gut wall changes the electrical conductance as expected for a cation-selective epithelium. The effect of a mucosa to serosa current on the Jms value of mannitol provides confirmation of the expected current effect on transepithelial volume flow. These effects on conductance and solute flux, together with the electrostatic effect on lysine movements, suffice to account for the p.d. effects on Jmc, Jms, and Jsm of lysine.4. JlYs is in a saturable manner stimulated by increasing concentrations of Dglucose. At higher (10 mM) concentrations of lysine this effect leads to a net secretion of lysine. Qualitatively and quantitatively these effects are consistent with the model of a glucose-induced fluid circuit between the mucosal solution and the lateral intercellular spaces.5. All observations are consistent with a paracellular, transepithelial pathway for lysine, which includes the lateral intercellular spaces.6. The transport of lysine across the basolateral membrane is analysed. Together the data on transcellular passage of lysine are very similar to those reported for rabbit ileum, except that more than one transport process could not be demonstrated.

Effects of dietary intake of sodium chloride on sugar and amino acid transport across isolated hen colon

“…It is, however, consistent with all the observations to propose that the mechanism responsible for the Na-sugar co-transport is abolished in the low Na colon, whereby the function of a transport system is revealed, which may be identical with the phloretin sensitive system described in the enterocyte of the chicken small intestine (Kimmich & Randles, 1975). Also in the case of lysine our results indicate that a mechanism responsible for cotransport with Na has disappeared, but the data of Fig eye to fit the raw data, which in all likelihood include a relatively, quite large fraction of paracellular diffusion (Munck & Rasmussen, 1979). The jLya may therefore well be reduced by a factor of about 10 compared to the high Na colon.…”

Lysine transport across the small intestine. Stimulating and inhibitory effects of neutral amino acids

“…The interactions between neutral (~-amino-monocarboxylic acids) and basic (diamino acids) during passage of the membranes of intestinal epithelia have been studied by sacs of everted intestine [7][8][9]20], by rings of everted intestine [26,28,29], by isolated mucosa [16], and by isolated intestinal cells [22 25], by measurements of unidirectional transepithelial fluxes, and by measuring influx across the brush border membrane [16,15]. In these different inhibitory and stimulating effects of neutral amino acids on the transport of basic amino acids have been observed.…”

Different pathways for lysine transport across neonatal pig intestine.

“…The curvilinear relation between lysine transport and concentration of free lysine in the mucosal solution is similar to that described previously for the rat jejunum, where the non-saturating portion of uptake has been said to take place by paracellular pathways (Munck & Rasmussen, 1979). Assuming this to be the case for the pig intestine, we have assessed its contribution to total flux by measuring the concentration dependence of the serosa to mucosa flux of lysine over the concentration range 1-20 mm.…”

“…Previous attempts to identify different routes for lysine absorption have led to the suggestion that lysine uses two carrier-mediated systems when entering the mucosa of the rabbit ileum (Munck & Schultz, 1969) and that there is a diffusional as well as a carrier-mediated flux of lysine across the rat 452 K. A. BURTON AND OTHERS jejunum, the diffusional component taking place through paracellular pathways (Munck & Rasmussen, 1979).…”