Addition Of Fructose Research Articles

Identification of irradiated dried fruits using EPR spectroscopy

Abstract The dominating carbohydrates in fruits are monosaccharides like fructose, glucose, sorbose and mannose. In dehydrated fruits, concentration of monosaccharides is higher than in fresh fruits resulting in the formation of sugar crystallites. In most of dried fruits, crystalline fructose, and glucose dominate and appear in proportion near to 1:1. Irradiation of dried fruits stimulates radiation chemical processes resulting in the formation of new chemical products and free radicals giving rise to multicomponent EPR signal which can be detected for a long period of time. For that reason, it is used as a marker for the detection of radiation treatment of dried fruits. It has been found that EPR spectra recorded in dried banana, pineapple, papaya, and fig samples resemble the EPR spectrum obtained by computer addition of fructose and glucose spectra taken in proportion 1:1. The decay of radiation induced EPR signals proceeds in dried fruits fast during the first month of observation and becomes much slower and almost negligible after prolonged storage. However, it remains intense enough for EPR detection even one year after processing. The radiation induced EPR signal is easily detected in dried fruits exposed to 0.5 kGy of gamma rays. Thus, the EPR method of the detection of irradiated fruits can be used for the control of dried fruits undergoing quarantine treatment with 200-300 Gy of ionizing radiation.

Cyclic AMP (cAMP) Receptor Protein-cAMP Complex Regulates Heparosan Production in Escherichia coli Strain Nissle 1917.

Heparosan serves as the starting carbon backbone for the chemoenzymatic synthesis of heparin, a widely used clinical anticoagulant drug. The availability of heparosan is a significant concern for the cost-effective synthesis of bioengineered heparin. The carbon source is known as the pivotal factor affecting heparosan production. However, the mechanism by which carbon sources control the biosynthesis of heparosan is unclear. In this study, we found that the biosynthesis of heparosan was influenced by different carbon sources. Glucose inhibits the biosynthesis of heparosan, while the addition of either fructose or mannose increases the yield of heparosan. Further study demonstrated that the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex binds to the upstream region of the region 3 promoter and stimulates the transcription of the gene cluster for heparosan biosynthesis. Site-directed mutagenesis of the CRP binding site abolished its capability of binding CRP and eliminated the stimulative effect on transcription. (1)H nuclear magnetic resonance (NMR) analysis was further performed to determine the Escherichia coli strain Nissle 1917 (EcN) heparosan structure and quantify extracellular heparosan production. Our results add to the understanding of the regulation of heparosan biosynthesis and may contribute to the study of other exopolysaccharide-producing strains.

Exploiting the Reaction of Cytochrome C with Fructose Dehydrogenase for a Multilayer Electrode Construction

The creation of analytical electron transfer (ET) chains based on the defined arrangement of enzymes and the redox protein cytochrome c (cyt c) on electrode surfaces represents an emerging field in bioelectronics.1,2 In this study we investigate the ET reaction of the flavin-dependent enzyme fructose dehydrogenase (FDH) with the redox protein cyt c. Two different pH optima are identified for the reaction with both proteins in solution, at acidic and neutral pH. When one reaction partner - cyt c - is immobilized on a modified gold electrode surface, ET proceeds efficiently at neutral pH which can be concluded from well shaped catalytic currents obtained in cyclic voltammograms. In addition a defined dependence on the substrate concentration is observed. In acidic media the reaction can also be verified but appears to be less efficient. This indicates that two different ET pathways between the enzyme and immobilized cyt c occur. Moreover, it is demonstrated that both partners can be assembled in a stable multilayer architecture, using the biopolymer DNA as connecting polyelectrolyte. The defined layered deposition of DNA with co-immobilized FDH and cyt c is verified by surface plasmon resonance (SPR) measurements. Prepared on electrodes, substantial catalytic currents are recorded upon addition of fructose. The response is found to be dependent on the number of layers deposited on the surface. This shows that an artificial signal chain can be constructed through multiple protein layers. Our results contribute to the better understanding of the ET-reaction between FDH and cyt c in a surface confined state, providing the basic knowledge which may be relevant for the creation of innovative fructose sensitive electrodes. 1. Lisdat, F.; Dronov, R.; Moehwald, H.; Scheller, F. W.; Kurth, D. G., Chemical Communications 2009, 274-283. 2. Feifel, S. C.; Kapp, A.; Lisdat, F., in Biosensors Based on Aptamers and Enzymes, Springer 2014, 140, 253-298.

Bacterial Cellulose as a Potential Bone Graft

Each year tissue engineering costs the United States $2 million dollars. Bacterial Cellulose (BC), a hydrogel with a ne ber network, is produced by the bacterium Acetobacter xylinum that can be used as a protective coating. In contrast to other polymers, BC possesses high tensile strength, high water holding capabilities, and high mechanical properties. The purpose of the current study is to determine if individual bers of BC can be functionalized with calcium by applying an electric eld. BC was grown and calcium was deposited simultaneously using Corn Steep Liquor (CSL) media, with the addition of fructose, in channels 4 cm long x 5 mm wide x 2.5 mm deep. The channels contained platinum electrodes supplying an electric eld of 3 to 7.5 volts for 72 hours in the presence of CaCl 2 . BC pellicles formed and were then examined using the Environmental Scanning Electron Microscope (ESEM). Energy-Dispersive X-ray Spectroscopy (EDS) was also used to determine the composition in each sample. Calcium was found deposited on the BC bers at 5.5 volts. Lower voltages, such as 4.0 volts, resulted in no calcium deposition on the bers. The presence of Carboxymethyl Cellulose (CMC) is critical for the calcium deposition. Calcium deposition will occur at 5.5 volts suggesting there may be a speci c electric eld requirement for calcium deposition on BC.

Synthesis, structural characterization, and tensile properties of fructose functionalized multi-walled carbon nanotubes/chitosan nanocomposite films

In this study, novel nanocomposite films of chitosan with fructose modified multi-walled carbon nanotube were prepared by solution casting technique. The fructose modified multi-walled carbon nanotube and the resulting bionanocomposite films were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, atomic force microscopy and transmission electron microscopy. The transmission electron microscopy showed that the presence of the functional moieties helped to improve the dispersion and compatibility of the multi-walled carbon nanotubes in the chitosan matrix. The tensile strength of bionanocomposite films was increased from 32 MPa for the pure chitosan film up to 62.96 MPa for the nanocomposite with 7 wt% addition of fructose modified multi-walled carbon nanotube.

English

Biodegradation of acid blue 113 has been studied using two strains-Staphylococcus aureus and Escherichia coli. The effect of pH, time, initial dye concentration, the inoculum size, the co-substrate, static and shaking on decolourisation was studied. The optimum condition for decolourisation was found to be at pH 7 for an initial dye concentration of 200 mg/L at 37 C under static condition. The removal of dye by S.aureus and E.coli at optimum condition was 90% and 88% within 30 h and 42 h respectively. Addition of fructose and starch as carbon source increased the removal of colour by S.aureus and E.coli respectively. Similarly addition of ammonium formate and glycine as nitrogen source under static condition increased the colour removal by S.aureus and E. coli. The enzyme activity of azoreductase for S. aureus and E. coli was found to be 7.33 U/ml and 7.24 U/ml respectively. The COD reduction, FTIR and TLC analysis of the sample before and after decolourisation confirmed the biodegradation of dye and the formation of new metabolite. Phytotoxicity studies indicated that the microbial treated effluent is safe for disposal into the environment.

Flavor compounds of Low-Fat Sausage Manufactured with Various Levels and Kinds of Sugar as a Fat Precursor

The objective of this study was performed to develop low-fat sausages(LFSs) with similar flavor profiles to those of regular-fat counterpart(RFC) using the addition of various kinds and levels of sugars in combined with 0.1 M lysine. Approximately 42 flavor compounds were identified and observed in most phenols, aldehydes, hetero compounds, ketones and alkans. Among them, phenols and aldehydes were the predominant flavor compounds and 28 flavor compounds were observed as affected by various kinds and levels of sugars. Although the volatile compounds such as 5-methyl furfural, 2-methoxy phenol, 2-methoxy-4-methyl phenol and 17-octadecenal were not different between the RFC and low-fat control(LFC), the addition of fructose and sucrose in combination with 0.1 M lysine affected the composition of volatile compounds in LFSs. Approximately 14 volatile compounds including 2-chloro-2-methyl butane, cyclopentanol, octane and furfural showed differences between RFC and LFC, but these differences were also reduced with the addition of sugars in combination with 0.1 M lysine. The volatile compounds such as nonanal, α-terpinene, myristicine, 2-pentadecanone, pentadecanal and octadecanal were not affected by the addition of sugars and lysine. However, the volatile compounds such as 2-methyl-2-butanol, 5-methyl furfural, 2-methoxy phenol, 2-methoxy-4-methyl phenol and 17-octadecenal were reduced with increased level of sugar.

A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH

Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka=3582.88M−1) and selectivity for fructose over glucose at pH=7.4. The sensor 1 showed a linear response toward d-fructose in the concentrations ranging from 2.5×10–5 to 4×10–4molL−1 with the detection limit of 1.3×10–5molL−1.

Sensory aroma characteristics of alcalase hydrolyzed rice bran protein concentrate as affected by spray drying and sugar addition.

The sensory aroma characteristics of alcalase hydrolyzed rice bran protein concentrate as affected by spray drying and sugar addition were investigated. Rice bran protein concentrate (RBPC) was hydrolyzed by alcalase. Sucrose, glucose or fructose was added to the liquid rice bran protein hydrolysate (LRBPH) and subsequently spray dried. The sensory aroma intensities of the hydrolysates were evaluated. Results showed that after spray drying, the rice bran protein concentrate powder (RBPC-P) had higher sweet and cocoa-like aroma intensities than RBPC (p ≤ 0.05) and hydrolyzed rice bran protein powder (HRBPP) had higher milk powder-like aroma intensities than LRBPH (p ≤ 0.05). The sweet, cocoa-like and milk powder-like aroma intensities in hydrolyzed rice bran protein powder with fructose addition (HRBPP-F) were significantly higher (p ≤ 0.05) than those of hydrolyzed rice bran protein powder with sucrose or glucose addition (HRBPP-S or HRBPP-G). HRBPP-F had the highest overall aroma liking score. These results also indicate that spray drying and sugar addition could improve the sensory aroma characteristics of alcalase hydrolyzed RBPC.

Composition and occurrence of lipid droplets in the cyanobacterium Nostoc punctiforme.

Inclusions of neutral lipids termed lipid droplets (LDs) located throughout the cell were identified in the cyanobacterium Nostoc punctiforme by staining with lipophylic fluorescent dyes. LDs increased in number upon entry into stationary phase and addition of exogenous fructose indicating a role for carbon storage, whereas high-light stress did not increase LD numbers. LD accumulation increased when nitrate was used as the nitrogen source during exponential growth as compared to added ammonia or nitrogen-fixing conditions. Analysis of isolated LDs revealed enrichment of triacylglycerol (TAG), α-tocopherol, and C17 alkanes. LD TAG from exponential phase growth contained mainly saturated C16 and C18 fatty acids, whereas stationary phase LD TAG had additional unsaturated fatty acids characteristic of whole cells. This is the first characterization of cyanobacterial LD composition and conditions leading to their production. Based upon their abnormally large size and atypical location, these structures represent a novel sub-organelle in cyanobacteria.

Vanadium methyl-bipyridine organoligand and its influence on energy balance and organs mass.

In the treatment of lifestyle diseases, including metabolic syndrome and type 2 diabetes, it is important to lower body mass and fat tissue, and consequently, to increase insulin-sensitivity. Unfortunately, it often happens that low-energy diet which would lower overweight is not observed and, thus, it does not bring the expected effects. This paper discusses the influence of three diets—control, high-fructose, and high-fatty diet—on absorption of energy from food in order to transform it into body mass. The kJ/g ratio which describes this process has been calculated. In the tested diets, the addition of fructose (79.13 ± 2.47 kJ/g) or fat (82.48 ± 2.28 kJ/g) results in higher transformation of energy into body mass than in the case of control diet (89.60 ± 1.86 kJ/g). The addition of Na[VO(O2)2(4,4′-Me2-2,2′-bpy)]•8H2O (where 4,4′-Me2-2,2′-bpy = 4,4′-dimethyl-2,2′-bipyridine) results in statistical increase of that ratio: fructose diet (86.88 ± 0.44 kJ/g), fat diet (104.68 ± 3.01 kJ/g), and control diet (115.98 ± 0.56 kJ/g), respectively. Fat diet statistically influences the decrease of kidney mass in comparison to the other diets. The application of the tested vanadium compound results also in the statistical decrease of the fatty liver caused by fructose and fat diet.

Effect of sugars and salts on rheological properties of Balangu seed (Lallemantia royleana) gum

The effect of different sugars (sucrose, glucose, fructose, and lactose) and salts (NaCl and CaCl2) at various concentrations on rheological properties of Balangu seed gum (BSG, 1% w/w) was investigated. The apparent viscosity was influenced by the sugars and salts concentration and shear rate. Synergistic interaction between BSG gum and sugars improved the viscosity of solutions, whereas addition of salts decreased viscosity of gum solutions. The Power law and Herschel–Bulkley models were fitted to shear stress–shear rate data to obtain the consistency coefficient (K) and flow behavior index (n) for BSG solutions. Power law model well described non-Newtonian pseudoplastic behavior of BSG. Both K and n were sensitive to sugars and salts concentration. Highest values (0.45–0.49) of flow behavior index were observed for glucose at all concentrations. Addition of sucrose, fructose, lactose and salts to BSG led to more pseudoplastic solutions, whereas glucose decreased pseudoplasticity of solutions.

Phase Equilibria of Carbon Dioxide, Propane Hydrate in the Presence of Glucose and Fructose

Phase equilibrium data for the hydrates formed in four three-component systems: CO2 + glucose + water system, CO2 + fructose + water system, C3H8 + glucose + water system, C3H8 + fructose + water system were measured in pressures range of (0.24 to 4.57 MPa) and temperatures range of (274.9 to 283.1 K) at 5% and 10% mass fraction of additives. The experimental data were determined using an isochoric pressure-search method. The effects of glucose (or fructose) on CO2 and C3H8 hydrate formation condition were studied. The addition of glucose or fructose increase the equilibrium pressure of the CO2 and C3H8 to form hydrate, and the presence of 10 mass% concentration of glucose (or fructose) showed more remarkable inhibition effect on CO2 and C3H8 hydrate formation.

Fructose-Mediated Elevation of Hydrogen Production in Glucose Tolerant Mutant of Synechocystis Sp. Strain PCC 6803 under the Dark Anaerobic Nitrate-Free Condition

Fructose is a potential additive that elevates a supply of electrons to hydrogenase for hydrogen production in cyanobacteria. A series of dark anaerobic hydrogen production experiments was performed to evaluate the validity of this assumption, in which fructose from 0 to 110 mmol/L was added to HEPES buffer solution on which a glucose tolerant mutant of unicellular cyanobacterium Synechocystis sp. strain PCC 6803 (GT strain) was incubated. Despite the reported knowledge that fructose was an inhibitor for photoheterotrophic growth of Synechocystis cells, GT strain assimilated fructose and represented a limited heterotrophic growth on fructose in HEPES buffer solution under dark anaerobic condition. The initial hydrogen production rate that was 0.025 mmol/L h in run without fructose increased to 0.0917 mmol/L h in run with 60-83 mmol/L fructose. The associated increase in the initial amount of endogenous glucose from 0.22 mmol/L in run without fructose to 0.36 mmol/L in run with 50 mmol/L fructose was observed. Fructose released the complete suppression of hydrogen production by nitrate. This work presents the first experimental evidence that cells of GT strain are able to assimilate fructose for cell growth in dark anaerobic condition. Our results show that hydrogen production in Synechocystis sp. strain can be significantly elevated by a proper addition of fructose to dark anaerobic HEPES buffer solution.

Fructose Stimulates Na/H Exchange Activity and Sensitizes the Proximal Tubule to Angiotensin II

The proximal nephron reabsorbs 60% to 70% of the fluid and sodium and most of the filtered bicarbonate via Na/H exchanger 3. Enhanced proximal nephron transport is implicated in hypertension. Our findings show that a fructose-enriched diet causes salt sensitivity. We hypothesized that fructose stimulates luminal Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. Na/H exchange was measured in rat proximal tubules as the rate of intracellular pH (pHi) recovery in fluorescent units/s. Replacing 5 mmol/L glucose with 5 mmol/L fructose increased the rate of pHi recovery (1.8±0.6 fluorescent units/s; P<0.02; n=8). Staurosporine, a protein kinase C inhibitor, blocked this effect. We studied whether this effect was because of the addition of fructose or removal of glucose. The basal rate of pHi recovery was first tested in the presence of a 0.6-mmol/L glucose and 1, 3, or 5 mmol/L fructose added in a second period. The rate of pHi recovery did not change with 1 mmol/L but it increased with 3 and 5 mmol/L of fructose. Adding 5 mmol/L glucose caused no change. Removal of luminal sodium blocked pHi recovery. With 5.5 mmol/L glucose, angiotensin II (1 pmol/L) did not affect the rate of pHi recovery (change, -1.1±0.5 fluorescent units/s; n=9) but it increased the rate of pHi recovery with 0.6 mmol/L glucose/5 mmol/L fructose (change, 4.0±2.2 fluorescent units/s; P<0.02; n=6). We conclude that fructose stimulates Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. This mechanism is likely dependent on protein kinase C. These results may partially explain the mechanism by which a fructose diet induces hypertension.

Consumption of a Diet Low in Advanced Glycation End Products for 4 Weeks Improves Insulin Sensitivity in Overweight Women

OBJECTIVE High-heat cooking of food induces the formation of advanced glycation end products (AGEs), which are thought to impair glucose metabolism in type 2 diabetic patients. High intake of fructose might additionally affect endogenous formation of AGEs. This parallel intervention study investigated whether the addition of fructose or cooking methods influencing the AGE content of food affect insulin sensitivity in overweight individuals. RESEARCH DESIGN AND METHODS Seventy-four overweight women were randomized to follow either a high- or low-AGE diet for 4 weeks, together with consumption of either fructose or glucose drinks. Glucose and insulin concentrations-after fasting and 2 h after an oral glucose tolerance test-were measured before and after the intervention. Homeostasis model assessment of insulin resistance (HOMA-IR) and insulin sensitivity index were calculated. Dietary and urinary AGE concentrations were measured (liquid chromatography tandem mass spectrometry) to estimate AGE intake and excretion. RESULTS When adjusted for changes in anthropometric measures during the intervention, the low-AGE diet decreased urinary AGEs, fasting insulin concentrations, and HOMA-IR, compared with the high-AGE diet. Addition of fructose did not affect any outcomes. CONCLUSIONS Diets with high AGE content may increase the development of insulin resistance. AGEs can be reduced by modulation of cooking methods but is unaffected by moderate fructose intake.

Effect of heat treatment, pH, sugar concentration, and metal ion addition on green color retention in homogenized puree of Thompson seedless grape

Homogenized puree of Thompson seedless (Vitis vinifera ‘Thompson Seedless’) grape was treated under different conditions, including heating time (5–30 min), temperature (20–80 °C) and pH (2–10). Treatments with separate additions of glucose, fructose, and sucrose at concentrations of 100–600 g/L and salts of MgCl2, ZnCl2, GuSO4, and KCl at concentration of 1 g/L were also tested at 20 °C up to 30 min. Relative chlorophyll pigment retention (CR) was measured at 664 nm. The chlorophyll pigments were the most stable at 20 °C and the nature pH of grape puree (pH 3.4). Increasing temperature and changing pH reduced CR. After 30 min treatment at 80 °C, CR decreased to lower than 20% and 50% at pH 2 and 5, separately. Increasing fructose and sucrose concentrations reduced CR at pH 3, but increased it at most levels at pH 4. Increasing glucose concentration protected chlorophyll pigment from reduction in some cases at pH 3 and 4. CR increased with addition of metal ions increased at pH 4, but decreased at pH 3. Conditions of 23.3 °C, pH 4.5, and 120 g/kg fructose and 210 g/kg glucose produced the highest CR value.

Synergy of Boron Containing Solid Wastes and Fructose for the Production of Lightweight Aggregates: Microstructure and Properties

In Turkey 400,000 t/year of boron containing solid wastes are produced. The production of lightweight aggregates is a promising way to valorise these wastes. In the development of a suitable process the main disadvantage is borate migration towards the surface of the green pellets that causes excessive liquid phase formation during firing and subsequent sticking of the aggregates together or with the refractory lining of the kiln. In order to address this problem, fructose was added in the raw mix as a migration inhibitor, in 0.5 and 3.0 wt% respectively. The results have shown that 3.0 wt% of fructose lead to a sticky plastic mass whereas the pellets present no volume expansion during firing. The optimal results were obtained for 0.5 wt% of fructose addition, which inhibited the salt formation and a glassy impervious layer was formed after firing. For abrupt heating at 720 and 760 °C for 2 min, pellets were produced with porosity varying from 58 to 63 % and bulk density from 0.8 to 0.9 g/cm3. The individual compressive strength value of these samples was measured at 0.18 and 0.39 MPa, for 720 and 760 °C, respectively. The microstructure is comprised predominantly of a matrix with extended vitrified regions with both open and closed pores. Taking into account the relative low compressive strength values and the high water absorption, the possible applications of the boron containing lightweight aggregates could be insulation, geotechnical application, gardening and/or horticulture.

Direct determination of Cd, Pb and Cr in honey by slurry sampling electrothermal atomic absorption spectrometry

Slurry sampling electrothermal atomic absorption spectrometry was used for direct determination of Cr, Pb and Cd in honey without sample pretreatment. The honey slurries were prepared in aqueous solution containing hydrogen peroxide and nitric acid. The slurries were directly introduced in the pyrolytic graphite tubes. Pd–Mg was used as a chemical modifier only for Cd determination. Analytical curves were performed with aqueous standards for Pb and Cr and with addition of fructose for Cd. The quantification limits for Cd, Pb and Cr were 2.0, 5.4 and 9.4ngg−1, respectively. Acceptable precision of the methodology was obtained through repeatability and intermediate precision. In the accuracy study, recoveries were satisfactory (94–101%) for the three elements. The methodology was applied in honey from Paraná (Brazil). The concentrations of Pb, Cd and Cr ranged from 141 to 228ngg−1, <2.0 to 8ngg−1 and 83 to 94ngg−1, respectively.

Abstract 41: Fructose Stimulates Na/H Exchanger 3 Activity and Enhances the Ability of Angiotensin II to Activate Na/H Exchanger 3 in the Proximal Tubule

Consumption of high-fructose corn syrup as a sweetener has increased dramatically. Fructose has been implicated in the epidemic of diabetes, obesity and hypertension including salt-sensitive hypertension. However, the mechanisms are poorly understood. The proximal nephron reabsorbs 60-70% of the fluid and Na, and most of the filtered bicarbonate via Na/H exchanger 3. Enhanced proximal nephron transport has been implicated in several forms of hypertension. We hypothesized that fructose stimulates NHE3 activity and enhances the ability of angiotensin II (ANG II) to activate NHE3 in the proximal tubule. To test our hypothesis we isolated and perfused proximal tubules from Sprague Dawley rats. NHE3 activity was measured as the recovery of intracellular pH after an NH4Cl acid pulse using the pH sensitive dye BCECF. The rate of pH recovery was measured in Fluorescent Units per second (FU/sec). In the presence of a 5.5 mM glucose-containing physiological saline the basal rate of pH recovery was 3.1 ± 0.8 FU/sec. When the luminal solution was exchanged to a 0.6 mM glucose + 5 mM fructose-containing physiological saline in a second period, the rate of pH recovery increased to 5 ± 1 FU/sec (p&lt;0.03, n=8).To study whether this effect was due to the addition of fructose or the removal of glucose to the lumen, we performed a separate set of experiments where 5 mM glucose was substituted for 5 mM fructose. In the presence of 0.6 mM glucose the basal rate of pH recovery was 3.6 ± 1.5 FU/sec. When 5 mM fructose was added the rate of pH recovery increased to 5.9 ± 2 FU/sec (p&lt;0.02, n=5). Control experiments showed no differences between periods when 5 mm glucose was added back to the luminal perfusate. Finally, we tested the effect of low concentrations of ANG II in the presence or absence of luminal fructose. In the presence of 5.5 mM glucose, ANG II 10-12 M did not affect the rate of pH recovery (change: -1.1 ± 0.5 FU/sec, n=9). However, in the presence of 5 mM fructose, ANG II increased the rate of pH recovery (change: 4.0 ± 2.2 FU/sec, p&lt; 0.03 n=6). We conclude that acute treatment with fructose stimulates NHE3 activity and enhances the ability of ANG II to activate NHE3 in the proximal tubule. These results may partially explain the mechanism by which a fructose diet induces hypertension.