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

Abstract

SUMMARY1. Using the isolated mucosa from the colon ofthe adult hen, transport of galactose, leucine and lysine was studied through measurements of influx across the brushborder membrane, unidirectional transmucosal fluxes, and of steady-state mucosal uptake.2. In hens maintained on a NaCl rich diet influx of galactose, leucine and lysine were saturable processes with well defined values for Jmax and Kt. All three substances were actively transported across the epithelium and accumulated in the mucosal tissues to steady-state concentrations several times higher than in the incubation media.3. In hens maintained on a NaCl poor diet the Kt of the leucine influx was markedly increased and the Jmax moderately decreased, while the epithelium maintained the capability of active transepithelial transport and of establishing a steady-state tissue/medium distribution ratio well above 1. Galactose and lysine could no longer be actively transported and in the steady state their tissue concentrations did not exceed those of the medium.4. It is proposed that in the low NaCl colon the processes of galactose and lysine cotransport with Na are abolished and that the transport of galactose proceeds via a phloretin sensitive system like that described for the enterocyte of the chicken small intestine.5. In the high NaCl colon 1 mM-leucine increases the mucosa to serosa flux of lysine by a factor 2-8 without affecting the serosa to mucosa flux or the steady-state mucosal accumulation of lysine. In the low NaCl colon 1 mM-leucine induces active transepithelial transport of lysine. Assuming that the active transport of leucine is secondary to the transport of Na, leucine-induced active transport of lysine is described as a tertiary active transport.6. In the high NaCl colon the mucosa to serosa flux and the steady-state mucosal accumulation of leucine were inhibited by galactose which had no effect on leucine influx across the brush-border membrane. Leucine did not affect any of the parameters of galactose transport.

Effects of sugars, amino acids and inhibitors on electrolyte transport across hen colon at different sodium chloride intakes.

“…For the low Na colon the results indicate that Na coupled transport of sugars and lysine cannot be accomplished. Lind, Munck & Olsen (1980) have confirmed the validity of these interpretations. In a variety of colonic mucosae availability of glucose to the tissues plays a crucial role for the maintenance of the I8, (Binder & Rawlins, 1973;Thompson & Dawson, 1978;Frizzell, Koch & Schultz, 1976).…”

Effects of Resalination on Intestinal Glucose Transport in Chickens Adapted to Low Na+ Intakes

“…The changes in transepithelial Na¤ movements according to dietary NaCl are correlated with changes in plasma aldosterone (Skadhauge, 1993). The intestinal co-transport of Na¤ with certain nutrients is also sensitive to the NaCl status; thus, Lind et al (1980) observed that glucose-and amino acid-induced short-circuit current across the rectum was abolished in NaCl-depleted chickens. It was later demonstrated that rectal enterocytes lose the capacity to accumulate hexoses (Jaso et al 1995) due, among other factors, to a decrease in apical SGLT1 expression (Bindslev et al 1997;Garriga et al 1998).…”

“…All regions of the lower intestine also contribute to the resorption of ureteral electrolyte and fluid (Skadhauge, 1993). Furthermore, the proximal caecum and the rectum can also absorb Na¤ cotransported with glucose and amino acids (Lind et al 1980;Moret o & Planas, 1989;Ferrer et al 1994b;Amat et al 1999). All these functions are affected by the NaCl status of the animal since restriction of Na¤ intake results in adaptive regulation, especially in the lower intestine, where there is a marked increase in the apical epithelial Na¤ channel (ENaC; Goldstein et al 1997) and the Na¤-H¤ exchanger (NHE2; Donowitz et al 1998) activities, and in the short-circuit current (Thomas & Skadhauge, 1982;Amat et al 1988).…”

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

“…However, the results of our experiment indicate that increased amino acid concentration not always caused increased absorption. The presence of glucose (Olszewski, 1975) or sodium and potassium ions (Robinson et al, 1973;Lind et al, 1980;Munck, 1981) were found to play important role in the absorption of some amino acids from the caecum or colon of sheep, dog or chicken. Such data support the active or facilitated character of the absorption process.…”