The comparative effects of some phlorizin analogs on the renal reabsorption of glucose

Diedrich, Donald F.

doi:10.1016/0006-3002(63)91142-9

Cited by 39 publications

(15 citation statements)

References 17 publications

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“…Phlorizin undergoes a keto‐enol tautomerization (Diedrich, 1963), with the enol ‐tautomer favoured at high pH and the keto ‐tautomer being most abundant at low pH. At the normal pH of 7.5 0.2 μ M phlorizin completely inhibited the 0.4 m M αMDG‐dependent current and the uncoupled Na ‘leak’ current through hSGLT1 (not shown).…”

Section: Resultsmentioning

confidence: 99%

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters

Hirayama

Dı́ez-Sampedro

Wright

2001

British J Pharmacology

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1 Electrophysiological methods were used to investigate the interaction of inhibitors with the human Na + /glucose (hSGLT1) and Na + /Cl 7 /GABA (hGAT1) cotransporters. Inhibitor constants were estimated from both inhibition of substrate-dependent current and inhibitor-induced changes in cotransporter conformation. 2 The competitive, non-transported inhibitors are substrate derivatives with inhibition constants from 200 nM (phlorizin) to 17 mM (esculin) for hSGLT1, and 300 nM (SKF89976A) to 10 mM (baclofen) for hGAT1. At least for hSGLT1, values determined using either method were proportional over 5-orders of magnitude. 3 Correlation of inhibition to structure of the inhibitors resulted in a pharmacophore for glycoside binding to hSGLT1: the aglycone is coplanar with the pyranose ring, and binds to a hydrophobic/ aromatic surface of at least 7612A Ê . Important hydrogen bond interactions occur at ®ve positions bordering this surface. 4 In both hSGLT1 and hGAT1 the data suggests that there is a large, hydrophobic inhibitor binding site *8A Ê from the substrate binding site. This suggests an architectural similarity between hSGLT1 and hGAT1. There is also structural similarity between non-competitive and competitive inhibitors, e.g., phloretin is the aglycone of phlorizin (hSGLT1) and nortriptyline resembles SKF89976A without nipecotic acid (hGAT1). 5 Our studies establish that measurement of the eect of inhibitors on presteady state currents is a valid non-radioactive method for the determination of inhibitor binding constants. Furthermore, analysis of the presteady state currents provide novel insights into partial reactions of the transport cycle and mode of action of the inhibitors.

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Section: Resultsmentioning

confidence: 99%

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters

Hirayama

Dı́ez-Sampedro

Wright

2001

British J Pharmacology

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“…Since the phloretin moiety in the phlorizin molecule is required to observe high affinity binding to the Na+-o-glucose cotransporter it has been proposed that phlorizin may interact with two points at the Dglucose binding site [1,6]. To test this hypothesis we measured whether phloretin, which is a noncompetitive inhibitor of Na+-D-glucose cotransport [7], is able to competitively inhibit phlorizin binding to brush-border membrane vesicles from outer renal cortex.…”

Section: Inhibition Of Phlor1z1n Equilibrium Binding By Phloretinmentioning

confidence: 98%

“…This latter fraction of nonspecific binding was calculated from the linear increase of phlorizin binding which was observed after the nonspecific phlorizin measured in the presence of 5 mM nonlabeled phlorizin had been subtracted. 6 Since the second fraction of nonspecific binding increased with time it was calculated separately for the different times of phlorizin incubation used in the experiments. 7 In Figs.…”

Section: Measurement Of the Onset Of Phlorizin Bindingmentioning

confidence: 99%

Two substrate sites in the renal Na+-d-glucose cotransporter studied by model analysis of phlorizin binding and-d-glucose transport measurements

et al. 1990

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Time courses of phlorizin binding to the outside of membrane vesicles from porcine renal outer cortex and outer medulla were measured and the obtained families of binding curves were fitted to different binding models. To fit the experimental data a model with two binding sites was required. Optimal fits were obtained if a ratio of low and high affinity phlorizin binding sites of 1:1 was assumed. Na+ increased the affinity of both binding sites. By an inside-negative membrane potential the affinity of the high affinity binding site (measured in the presence of 3 mM Na+) and of the low affinity binding site (measured in the presence of 3 or 90 mM Na+) was increased. Optimal fits were obtained when the rate constants of dissociation were not changed by the membrane potential. In the presence of 90 mM Na+ on both membrane sides and with a clamped membrane potential, KD values of 0.4 and 7.9 microM were calculated for the low and high affinity phlorizin binding sites which were observed in outer cortex and in outer medulla. Apparent low and high affinity transport sites were detected by measuring the substrate dependence of D-glucose uptake in membrane vesicles from outer cortex and outer medulla which is stimulated by an initial gradient of 90 mM Na+ (out greater than in). Low and high affinity transport could be fitted with identical Km values in outer cortex and outer medulla. An inside-negative membrane potential decreased the apparent Km of high affinity transport whereas the apparent Km of low affinity transport was not changed. The data show that in outer cortex and outer medulla of pig high and low affinity Na(+)-D-glucose cotransporters are present which contain low and high affinity phlorizin binding sites, respectively. It has to be elucidated from future experiments whether equal amounts of low and high affinity transporters are expressed in both kidney regions or whether the low and high affinity transporter are parts of the same glucose transport molecule.

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“…Phlorizin is a ␤-glucoside comprised of two aromatic rings (A and B) joined by an alkyl spacer of three carbons. As with the aglycone phloretin, it undergoes a keto-enol tautomerization (52, 242), with the keto-form being the higher affinity configuration (32,66).…”

Section: Inhibitorsmentioning

confidence: 99%

Biology of Human Sodium Glucose Transporters

Wright

Loo

Hirayama

2011

Physiological Reviews

1,209

1,269

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There are two classes of glucose transporters involved in glucose homeostasis in the body, the facilitated transporters or uniporters (GLUTs) and the active transporters or symporters (SGLTs). The energy for active glucose transport is provided by the sodium gradient across the cell membrane, the Na(+) glucose cotransport hypothesis first proposed in 1960 by Crane. Since the cloning of SGLT1 in 1987, there have been advances in the genetics, molecular biology, biochemistry, biophysics, and structure of SGLTs. There are 12 members of the human SGLT (SLC5) gene family, including cotransporters for sugars, anions, vitamins, and short-chain fatty acids. Here we give a personal review of these advances. The SGLTs belong to a structural class of membrane proteins from unrelated gene families of antiporters and Na(+) and H(+) symporters. This class shares a common atomic architecture and a common transport mechanism. SGLTs also function as water and urea channels, glucose sensors, and coupled-water and urea transporters. We also discuss the physiology and pathophysiology of SGLTs, e.g., glucose galactose malabsorption and familial renal glycosuria, and briefly report on targeting of SGLTs for new therapies for diabetes.

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The comparative effects of some phlorizin analogs on the renal reabsorption of glucose

Cited by 39 publications

References 17 publications

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters

Two substrate sites in the renal Na+-d-glucose cotransporter studied by model analysis of phlorizin binding and-d-glucose transport measurements

Biology of Human Sodium Glucose Transporters

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The comparative effects of some phlorizin analogs on the renal reabsorption of glucose

Cited by 39 publications

References 17 publications

Common mechanisms of inhibition for the Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters

Common mechanisms of inhibition for the Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters

Two substrate sites in the renal Na+-d-glucose cotransporter studied by model analysis of phlorizin binding and-d-glucose transport measurements

Biology of Human Sodium Glucose Transporters

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Product

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About

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters

Common mechanisms of inhibition for the Na⁺/glucose (hSGLT1) and Na⁺/Cl⁻/GABA (hGAT1) cotransporters