Sodium-independent, hydrogen ion-dependent changes in membrane potential and conductance induced by dipeptides in Triturus enterocytes.

Abstract

The effects of Na+ and pH in the medium on dipeptide transport across Triturus small intestinal brush border membrane were studied electrophysiologically. Although glycylglycine exists mainly in the zwitterionic form at pH 7.30, it induced marked depolarization in the membrane potential and reduction in the input resistance both in the presence and absence of Na+ in the medium. Similar Na + -independent depolarization and resistance change were also observed with L-carnosine. On the contrary, glycine induced membrane depolarization and reduction in the input resistance only in the presence of Na + in the medium. When pH of the medium was lowered to 6.00, the magnitude of the depolarization induced by glycylglycine increased by 33%, while at pH 8.30, it decreased by 39%. These data indicate that dipeptide transport across the intestinal brush border membrane is coupled with H + and has no direct interaction with Na + .

Factors affecting the microclimate pH in rat jejunum.

“…Na+-independent and pH-dependent electrical responses to dipeptides in amphibian small intestines were also demonstrated * Present address: Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Tokyo 113, Japan. (Shimada & Hoshi, 1986a;Hoshi, 1986). As the transport of intact di-and tripeptides across the brush-border membrane has an important physiological role in the intestinal absorption of protein hydrolysates (Adibi & Kim, 1981), the H+ gradient across the brush-border membrane has attracted the renewed attention of investigators.…”

Characteristics of transmural potential changes associated with the proton‐peptide co‐transport in toad small intestine.

“…In these vesicles, glycyl-dipeptides, such as Gly-Pro, Gly-Sar and Gly-Gly, have been shown to cause depolarization of the membrane potential which can be visualized by a change in fluorescence of a membrane potential-sensitive dye, such as diS-C3-(5), added to the suspension medium (Ganapathy et al 1984;Takuwa et al 1985a, b). Also, Boyd & Ward (1982) and Shimada & Hoshi (1986) demonstrated that the transmembrane potential across the luminal membrane of intact amphibian intestinal epithelia was depolarized when dipeptides, such as Gly-Leu, Gly-Gly and carnosine, were added to Na+-free mucosal bathing solution, and that the depolarization was accompanied by a reduction of the input resistance. The pHo dependence of the amplitude of the depolarization was demonstrated by the latter authors (Shimada & Hoshi, 1986 In the present study, the coupling ratio of H+ current to dipeptide flux was determined to be approximately 2 (1P78 + 0-12).…”

“…Also, Boyd & Ward (1982) and Shimada & Hoshi (1986) demonstrated that the transmembrane potential across the luminal membrane of intact amphibian intestinal epithelia was depolarized when dipeptides, such as Gly-Leu, Gly-Gly and carnosine, were added to Na+-free mucosal bathing solution, and that the depolarization was accompanied by a reduction of the input resistance. The pHo dependence of the amplitude of the depolarization was demonstrated by the latter authors (Shimada & Hoshi, 1986 In the present study, the coupling ratio of H+ current to dipeptide flux was determined to be approximately 2 (1P78 + 0-12). A linear relationship between H+ and Gly-Gly influxes supports the idea that Gly-Gly transport is mediated by an H+-coupled co-transport, similar in mechanism of energy coupling to the Na+-coupled transport of D-glucose and amino acids.…”

Physiological Mechanisms of Intestinal Absorption of Protein Hydrolysates and Their Relevance to Bacterial Growth in the Small Intestine

“…The depolarizing responses were shown to be associated with an increase in membrane conductance. Both the depolarization and membrane conductance increase were independent of the presence of Na+ in the medium (2,18) . Lowering pH of the mucosal perfusion solution caused augmentation of the depolarizing response to dipeptides (18) .…”

“…Both the depolarization and membrane conductance increase were independent of the presence of Na+ in the medium (2,18) . Lowering pH of the mucosal perfusion solution caused augmentation of the depolarizing response to dipeptides (18) . Alkalinization of the perfusion solution resulted in the reverse change (diminution of the amplitude) even when the concentration of zwitterion dipeptide was made equal to that in control.…”