Studies on the mechanism of the intestinal absorption of sugars X. An effect of Na+ concentration on the apparent michaelis constants for intestinal sugar transport, in vitro

Crane, Robert K.; Forstner, G.; Eichholz, Alexander

doi:10.1016/0926-6585(65)90172-x

Cited by 175 publications

(45 citation statements)

References 44 publications

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“…Crane has attributed Csaky's finding of no sodium requirement at high glucose concentration to an additional effect of sodium, namely that the affinity of the carrier for glucose is increased. In support of this proposal he has demonstrated in vitro a dependence of the apparent Michaelis constant of sugar transport on the sodium concentration of the incubation fluid; Vmax was independent of the sodium concentration (34). Consequently, he felt that at very high sugar concentrations sodium would not be expected to have an effect.…”

Section: Methodsmentioning

confidence: 61%

The role of sodium in intestinal glucose absorption in man

Olsen¹,

Ingelfinger²

1968

J. Clin. Invest.

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Section: Methodsmentioning

confidence: 61%

The role of sodium in intestinal glucose absorption in man

Olsen¹,

Ingelfinger²

1968

J. Clin. Invest.

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“…A reduction of the external Na+ concentration did not change the apparent Km of the carrier for metaraminol but lowered the apparent Vmax (Sugrue & Shore, 1969b). Na+ had a similar effect on the transport of sugars by rabbit kidney slices (Kleinzeller, Kolinska & Benes, 1967) and by rabbit ileum (Goldner, Schultz & Curran, 1969) but a reduction in Na+ altered the Km and left the Vm.,, unchanged for sugar transport by hamster intestine (Crane, Forstner & Eichholz, 1965) and for amino-acid transport by rabbit lymph node cells (Kipnis & Parrish, 1965). It is possible that the adrenergic neurone membrane transport site for noradrenaline and metaraminol combines with both Na+ and amine to form a ternary complex.…”

Section: Discussionmentioning

confidence: 99%

Effects of Na⁺ and K⁺ on the uptake of metaraminol by rabbit ventricular slices

Paton

1971

British J Pharmacology

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4. The inhibitory effects on transport of either a marked reduction in the concentration of Na+ or of omission of K+ were rapidly reversible on exposure of slices to Krebs solution. 5. The inhibitory effect of ouabain on [3H]-metaraminol transport was markedly time dependent, being significantly increased by preincubation with ouabain. The inhibitory action of ouabain was not affected, however, by the Na+ concentration present during preincubation. 6. An inwardly directed Na+ gradient did not increase [3H]-metaraminol transport in slices in which Na+ pumiping had been prevented by 1O-5M ouabain, 40 C, omission of K+ or by metabolic inhibition. 7. These findings provide additional evidence that the Na+ and K+ activated adenosine triphosphatase may participate in the transport of metaraminol and related amines. In the absence of Na+ pumping, induced Na+ gradients were unable to produce transport of amine as would be predicted by the co-transport model proposed by . IntroductionTissues accumulate noradrenaline and structurally related compounds such as metaraminol, by a process which is temperature dependent, requires energy, is Na+ and K+ dependent and is inhibited by ouabain (Dengler, Michaelson, Spiegel &

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“…can be compared with those of Crane, Forstner, and Eichholz (15), who noted an eightfold reduction in in vitro 6-deoxyglucose transport when the sodium concentration was reduced from 145 to 24 mEq/liter (estimated from their Fig. 1, using a sugar concentration of 3.3 mM).…”

Section: Role Of Intraluminal Sodium In Glucose Absorption In Vivomentioning

confidence: 99%

The Role of Intraluminal Sodium in Glucose Absorption In Vivo

Saltzman¹,

Rector²,

Fordtran³

1972

J. Clin. Invest.

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A B S T R A C T Active glucose absorption is thought to depend on a gradient of sodium ion concentration across the brush border xnembrane of intestinal epithelial cells. This concept is generally accepted, although its validity has never been adequately evaluated in the human small intestine in vivo. According to this hypothesis, the rate of glucose absorption should decrease markedly if the luminal sodium concentration is markedly reduced, and glucose absorption against a concentration gradient should cease entirely if luminal sodium is lower than intracellular sodium concentration. In the present series of experiments we were not able to show an important role of intraluminal sodium concentration in the active absorption of glucose from the human, rat, and dog ileum in vivo. Specifically, glucose absorption was minimally reduced or not reduced at all when intraluminal sodium concentration was reduced from 140 to as low as 2.5 mEq/liter. The discrepancy between our results and those of previous workers whose data suggest that removal of intraluminal sodium should markedly inhibit active glucose absorption is not entirely clear, but there are a number of differences in experimental design between most previous studies and our own. Although our data show that active glucose absorption proceeds at a near normal rate even when lumen sodium concentration is reduced below 3 mEq/liter, our results do not disprove the sodium gradient theory because of the theoretic possibility that the microclimate adjacent to the brush border has a high concentration of sodium even when luminal sodium concentration is markedly reduced. The validity of the sodium gradient hypothesis would appear to be critically dependent on such a microclimate.

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Studies on the mechanism of the intestinal absorption of sugars X. An effect of Na+ concentration on the apparent michaelis constants for intestinal sugar transport, in vitro

Cited by 175 publications

References 44 publications

The role of sodium in intestinal glucose absorption in man

The role of sodium in intestinal glucose absorption in man

Effects of Na⁺ and K⁺ on the uptake of metaraminol by rabbit ventricular slices

The Role of Intraluminal Sodium in Glucose Absorption In Vivo

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Studies on the mechanism of the intestinal absorption of sugars X. An effect of Na+ concentration on the apparent michaelis constants for intestinal sugar transport, in vitro

Cited by 175 publications

References 44 publications

The role of sodium in intestinal glucose absorption in man

The role of sodium in intestinal glucose absorption in man

Effects of Na+ and K+ on the uptake of metaraminol by rabbit ventricular slices

The Role of Intraluminal Sodium in Glucose Absorption In Vivo

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Effects of Na⁺ and K⁺ on the uptake of metaraminol by rabbit ventricular slices