Studies on transmural potentials in vitro in relation to intestinal absorption I. Apparent michaelis constants for Na+-dependent sugar transport

Lyon, I.; Crane, Robert K.

doi:10.1016/0926-6585(66)90327-x

Cited by 89 publications

(19 citation statements)

References 24 publications

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“…The slower development of the amino acid potential reveals that the potential obtained consists of two components: (1) an osmotic component have shown that increase in mucosal osmotic pressure decreases the transmural potential), and (2) a component which is presumed to be associated with the transfer of the amino acid. Lyon & Crane (1966) have also suggested that there are two similar components in the hexose potential. In general, however, the osmotic component has not been taken into consideration in previous studies, and this may be of considerable importance for substances producing comparatively small changes in potential.…”

Section: Discussionmentioning

confidence: 99%

“…Following the procedure of Lyon & Crane (1966) the relationship between electric potential and concentration of amino acids has been studied by the application of methods formally similar to those of enzyme kinetics. In these the initial concentration (C) of amino acids in the mucosal fluid has been used, and the steady-state potential generated (P) is substituted for the rate of enzyme reaction.…”

Section: Methodsmentioning

confidence: 99%

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Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine

Kohn¹,

Smyth²,

Wright³

1968

The Journal of Physiology

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SUMMARY1. The effects of a number of amino acids, peptides and disaccharides on the potential difference across the wall of the rat small intestine have been studied.2. All the L-amino acids tested, except lysine and arginine, and the three D-amino acids tested stimulate the potential when present in the mucosal fluid.3. The concentration dependence and time course of the potential differs between different aminQ acids.4. The results suggest a close correlation between the active transport of an amino acid and the potential change which it evokes.5. Glycyl-glycine, glycyl-L-alanine and tri-glycine stimulate the potential and this appears to be due to the amino acids liberated by hydrolysis.6. Maltose and sucrose, but not lactose, stimulate the potential, and the effect appears to depend on the extent of hydrolysis of the disaccharide.7. The magnitude of the potential varies in different parts of the intestine. For the amino acids tested the maximum potential occurred in the distal ileum, while in the case of hexoses the maximum potential was found in the mid-intestine.8. The results are discussed in relation to the mechanisms of transfer of hexoses and amino acids. INTRODVCTIONIt is now well established that actively transported hexoses and amino acids in the lumen of the gut, or on the mucosal side of an everted sac

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine

Kohn¹,

Smyth²,

Wright³

1968

The Journal of Physiology

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“…Subsequent infusion of a series of solutions containing increasing concentrations of glucose (Table 1) by the determination of saturation kinetic parameters was initially borrowed from studies on enzyme substrate interactions (Fisher and Parsons, 1953;Smyth, 1971). Its further application to electrical measurements of transfer activity came from the in vitro studies of Asano (1964), Schultz and Zalusky (1964), and Lyon and Crane (1966). Debnam and Levin (1975a, b) extended its application to in vivo studies and showed that the 'Apparent Km' for the active electrogenic component of glucose absorption is the same whether calculated from measurements of hexose transfer PDs or from the chemically measured loss of glucose from the lumen.…”

Section: Subjectsmentioning

confidence: 99%

Electrogenic glucose absorption in untreated and treated coeliac disease.

Read¹,

Levin²,

Holdsworth³

1976

Gut

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SUMMARY Using a method for measuring changes in transmural potential difference across the human jejunum in vivo, the operational kinetic parameters of 'Apparent Km' and PD max for the active electrogenic component of glucose absorption were estimated in a group of healthy volunteers and in patients with coeliac disease. Both the 'Apparent Km' (17 2 mM; mean SEM) and the PD max (8.6 ± 0 7 mV) in nine patients with untreated coeliac disease were significantly lower (p < 0 005) than in the control group ('Apparent Km' = 74 ± 5 mM; PD max 12-8 ± 0-9 mV, n = 20). Treatment of five coeliac patients by gluten withdrawal for less than three months increased significantly the values of both the 'Apparent Km' (35 ± 6 mM) and the PD max (1li4 ± 1-2 mV). Treatment of five patients for more than six months caused a further increase in the values of both kinetic parameters ('Apparent Km' = 108 ± 13 mM; PD max = 15-6 ± 2-7 mV) to levels which exceeded those in healthy subjects. The possible interpretations of the differences in the kinetic characteristics of electrogenic glucose transport between coeliac patients and healthy subjects are discussed.

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“…In the guinea-pig, rat and hamster (Alvarado, 1976;Crane, Forstner & Eichholz, 1965;Lyon & Crane, 1966;van Melle & Robinson, 1981), the principal effect of alterations in the external sodium concentration appeared to be a change in Km ('K-kinetics'), whereas in the rabbit and chicken (Goldner, Schultz & Curran, 1969;Kimmich & Randles, 1975), changes in Vmax (' V-kinetics ') were reported. In contrast, all studies on the kinetics ofsodium-activated amino acid transport agree that the main effect of sodium is to reduce the Km for transport (Alvarado & Mahmood, 1974; Curran, Schultz, Chez & Fuisz, 1967; Sepulveda & Robinson, 1978).…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the sodium/beta‐methyl‐D‐glucoside co‐transport system in the guinea‐pig small intestine.

Robinson¹,

Melle²

1983

The Journal of Physiology

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SUMMARY1. Thekineticsofsodium-dependent,8-methyl-D-glucoside transportwere examined in guinea-pig intestinal rings. Large-scale experiments were performed in which both sodium and monosaccharide concentrations were varied within the same animal.2. The results were evaluated by non-linear regression analysis, and an attempt was made to distinguish between the applicability of different models to describe the data set.3. Only two of the tested models provided a good fit to the data. These both involved the random formation of a ternary complex from either intermediate binary complex; in one, the constraint that only the ternary complex was able to cross the membrane was included, whereas in the other the ratio of the permeability coefficients for the binary complex between sugar and carrier and for the ternary complex was estimated. But this ratio did not differ significantly from zero, so the two acceptable models were equivalent. In addition, it was necessary to introduce into both these models the concept of a sodium reservoir at the surface of the brush-border membrane, such that the local sodium concentration in the vicinity of the carriers could never fall below a certain critical value (which was estimated at 4-8 mM), even in complete absence of this ion from the bulk medium.

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Studies on transmural potentials in vitro in relation to intestinal absorption I. Apparent michaelis constants for Na+-dependent sugar transport

Cited by 89 publications

References 24 publications

Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine

Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine

Electrogenic glucose absorption in untreated and treated coeliac disease.

Kinetics of the sodium/beta‐methyl‐D‐glucoside co‐transport system in the guinea‐pig small intestine.

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