Influence of vascular and luminal hexoses on rat intestinal basolateral glucose transport

1994 ◽  
Vol 72 (4) ◽  
pp. 317-326 ◽  
Author(s):  
Raymond Tsang ◽  
Ziliang Ao ◽  
Chris Cheeseman
Keyword(s):  
Glucose Transport ◽  
Plasma Glucose ◽  
Intestinal Adaptation ◽  
Basolateral Membrane ◽  
Physiological Role ◽  
Intestinal Transport ◽  
Membrane Vesicles ◽  
Luminal Perfusion

The influence of luminal and vascular hexoses in rats on glucose transport across the jejunal basolateral membrane (BLM) was measured using isolated membrane vesicles prepared from infused animals. In vivo vascular infusions of glucose produced an increase in glucose transport across BLM vesicles. Sucrose, mannose, galactose, and fructose had no significant effect. Plasma glucose concentrations were unaffected by galactose and sucrose vascular infusions, while mannose and fructose produced a modest rise, and glucose increased plasma glucose to 20 mM. Insulin release was significantly increased by vascular infusion of glucose and fructose, while mannose produced only a small sustained rise. Sucrose and galactose had no effect. Perfusion through the lumen of the rat jejunum in vivo, for up to 4 h, with glucose, fructose, sucrose, or lactate (100 or 25 mM) produced a significant increase in the maximal rate of glucose transport (up to 4- to 5-fold) across BLMs. Galactose and mannose had no effect. Luminal glucose perfusion produced a small nonsignificant increase in glucose inhibitable cytochalasin B binding to BLM vesicles, and no change was seen in the microsomal pool of binding sites. The abundance of GLUT2 in the jejunal BLM, as determined by Western blotting, was unaffected by luminal perfusion of 100 mM glucose for 4 h. Fructose almost completely inhibited the carrier-mediated uptake of glucose in control and upregulated jejunal BLM vesicles. These results are discussed in relation to the physiological role of the upregulation of GLUT2 activity by luminal and vascular hexoses.Key words: intestinal transport, basolateral membrane, glucose transport, intestinal adaptation.

Polyamines alter intestinal glucose transport

1995 ◽  
Vol 268 (3) ◽  
pp. G416-G423 ◽  
Author(s):  
L. R. Johnson ◽  
P. D. Brockway ◽  
K. Madsen ◽  
J. A. Hardin ◽  
D. G. Gall
Keyword(s):  
Glucose Transport ◽  
Intestinal Transport ◽  
Membrane Vesicles ◽  
Membrane Lipid ◽  
Membrane Function ◽  
Polyamine Synthesis ◽  
Primary Activity

Polyamines are required for the growth of all eukaryotic cells. Enterocytes respond to luminal nutrients with large increases in polyamine synthesis, even though they are mature, nonproliferating cells. The role of polyamines in these cells is unknown. The current experiments examined whether polyamines affected intestinal transport of glucose, since absorption is the primary activity of enterocytes and since polyamines are known to affect membrane function and stability. Glucose transport was examined in rabbit brush-border membrane vesicles (BBMV). BBMV from rabbits given 5% alpha-difluoromethylornithine (DFMO) in their drinking water 24 h before they were killed transported significantly less glucose than control vesicles [38% decrease in maximal transport rate (Jmax)]. Orogastric administration of spermine, spermidine, or putrescine to DFMO-treated animals 24 h before they were killed prevented the decrease. In rabbits receiving only orogastric spermine, glucose transport was significantly increased (64% increase in Jmax), whereas in vivo spermidine and putrescine decreased Jmax. This increase in Jmax caused by in vivo administration of spermine was not dependent on protein synthesis. Addition of polyamines whether in vivo or in vitro decreased Michaelis constant in vesicles from control and DFMO-treated animals. The change in glucose transport induced by DFMO or polyamines was not related to altered membrane lipid composition or fluidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of intestinal glucose transport

1992 ◽  
Vol 70 (9) ◽  
pp. 1201-1207 ◽  
Author(s):  
D. J. Philpott ◽  
J. D. Butzner ◽  
J. B. Meddings
Keyword(s):  
Small Intestine ◽  
Glucose Transport ◽  
Intestinal Adaptation ◽  
Basolateral Membrane ◽  
Intestinal Transport ◽  
Glucose Absorption ◽  
Dietary Carbohydrate ◽  
Adaptive Responses ◽  
Carbohydrate Levels ◽  
Specific Regulation

The small intestine is capable of adapting nutrient transport in response to numerous stimuli. This review examines several possible mechanisms involved in intestinal adaptation. In some cases, the enhancement of transport is nonspecific, that is, the absorption of many nutrients is affected. Usually, increased transport capacity in these instances can be attributed to an increase in intestinal surface area. Alternatively, some conditions induce specific regulation at the level of the enterocyte that affects the transport of a particular nutrient. Since the absorption of glucose from the intestine is so well characterized, it serves as a useful model for this type of intestinal adaptation. Four potential sites for the specific regulation of glucose transport have been described, and each is implicated in different situations. First, mechanisms at the brush-border membrane of the enterocyte are believed to be involved in the upregulation of glucose transport that occurs in streptozotocin-induced diabetes mellitus and alterations in dietary carbohydrate levels. Also, factors that increase the sodium gradient across the enterocyte may increase the rate of glucose transport. It has been suggested that an increase in activity of the basolaterally located Na+–K+ ATPase could be responsible for this phenomena. The rapid increase in glucose uptake seen in hyperglycemia seems to be mediated by an increase in both the number and activity of glucose carriers located at the basolateral membrane. More recently, it was demonstrated that mechanisms at the basolateral membrane also play a role in the chronic increase in glucose transport observed when dietary carbohydrate levels are increased. Finally, alterations in tight-junction permeability enhance glucose absorption from the small intestine. The possible signals that prompt these adaptive responses in the small intestine include glucose itself and humoral as well as enteric nervous interactions.Key words: intestinal transport, glucose transport, intestinal adaptation.

Sulfate/oxalate exchange by lobster hepatopancreatic basolateral membrane vesicles

1995 ◽  
Vol 269 (3) ◽  
pp. R572-R577 ◽  
Author(s):  
G. A. Gerencser ◽  
M. A. Cattey ◽  
G. A. Ahearn
Keyword(s):  
Gradient Centrifugation ◽  
Basolateral Membrane ◽  
Physiological Role ◽  
Membrane Vesicles ◽  
Disulfonic Acid ◽  
Basolateral Membrane Vesicles ◽  
Sulfate Uptake ◽  
Discontinuous Sucrose Gradient ◽  
Carboxylic Anions

Purified basolateral membrane vesicles (BLMV) were prepared from lobster hepatopancreas by osmotic disruption and discontinuous sucrose gradient centrifugation. Radiolabeled sulfate uptake was stimulated by 10 mM intravesicular oxalate compared with gluconate-loaded vesicles. Sulfate/oxalate exchange was not affected by transmembrane valinomycin-induced potassium diffusion potentials (inside negative or inside positive), suggesting electroneutral anion transport. Sulfate uptake was not stimulated by the similar carboxylic anions formate, succinate, oxaloacetate, or ketoglutarate. Sulfate influx occurred by at least one saturable Michaelis-Menten carrier system [apparent Km = 6.0 +/- 1.7 mM; maximum flux (Jmax) = 382.3 +/- 37.0 pmol.mg protein-1 x 7 s-1]. Sulfate/oxalate exchange was significantly reduced by the anion antiport inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid but was not affected by bumetanide or furosemide. The possible physiological role of this exchange mechanism in anion/sulfate transport across the crustacean hepatopancreas is discussed.

Rapid regulation of D-glucose transport in basolateral membrane of rat jejunum

1989 ◽  
Vol 256 (5) ◽  
pp. G878-G883 ◽  
Author(s):  
C. I. Cheeseman ◽  
D. D. Maenz
Keyword(s):  
Glucose Uptake ◽  
Glucose Transport ◽  
Cytochalasin B ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Fold Increase ◽  
Glucose Infusion ◽  
Transport Activity ◽  
Site Density

D-Glucose transport and D-glucose inhibitable [3H]cytochalasin B binding to jejunal basolateral membrane vesicles were measured to investigate the possible association between changes in transport activity seen in hyperglycemia and density of transporter sites. Comparison was made between hyperglycemic animals, noninfused rats, and a group infused with sorbitol. Vascular infusion of D-glucose produced a rapid increase in D-glucose transport followed by a delayed and smaller increase in [3H]cytochalasin B binding. The Vmax for glucose uptake was increased after only 30 min of glucose infusion and continued to rise up to 6 h. Comparison with noninfused and sorbitol-infused controls showed that 2 h of glucose infusion produced a 3.5-fold increase in the Vmax for D-glucose uptake while D-glucose-inhibitable binding of [3H]cytochalasin B was unaffected. Six hours of hyperglycemia resulted in the further stimulation of glucose transport (4.1-fold) and a significant 1.8-fold increase in cytochalasin B binding over that for noninfused animals. Vesicles prepared from animals 4 h after an in vivo injection of cycloheximide showed an 80% reduction in glucose transport with no significant change in the cytochalasin B binding density. These results suggest that D-glucose transport in the basolateral membrane is regulated by a combination of a modulation of carriers already in the membrane and subsequent changes in carrier site density.

scholarly journals Purinergic Modulation of Interleukin-1β Release from Microglial Cells Stimulated with Bacterial Endotoxin

1997 ◽  
Vol 185 (3) ◽  
pp. 579-582 ◽  
Author(s):  
Davide Ferrari ◽  
Paola Chiozzi ◽  
Simonetta Falzoni ◽  
Stefania Hanau ◽  
Francesco Di  Virgilio
Keyword(s):  
Plasma Membrane ◽  
P2x7 Receptor ◽  
Purinergic Receptor ◽  
Present Report ◽  
Physiological Role ◽  
Bacterial Endotoxin ◽  
Microglial Cells

Microglial cells express a peculiar plasma membrane receptor for extracellular ATP, named P2Z/P2X7 purinergic receptor, that triggers massive transmembrane ion fluxes and a reversible permeabilization of the plasma membrane to hydrophylic molecules of up to 900 dalton molecule weight and eventual cell death (Di Virgilio, F. 1995. Immunol. Today. 16:524–528). The physiological role of this newly cloned (Surprenant, A., F. Rassendren, E. Kawashima, R.A. North and G. Buell. 1996. Science (Wash. DC). 272:735–737) cytolytic receptor is unknown. In vitro and in vivo activation of the macrophage and microglial cell P2Z/P2X7 receptor by exogenous ATP causes a large and rapid release of mature IL-1β. In the present report we investigated the role of microglial P2Z/P2X7 receptor in IL-1β release triggered by LPS. Our data suggest that LPS-dependent IL-1β release involves activation of this purinergic receptor as it is inhibited by the selective P2Z/P2X7 blocker oxidized ATP and modulated by ATP-hydrolyzing enzymes such as apyrase or hexokinase. Furthermore, microglial cells release ATP when stimulated with LPS. LPS-dependent release of ATP is also observed in monocyte-derived human macrophages. It is suggested that bacterial endotoxin activates an autocrine/paracrine loop that drives ATP-dependent IL-1β secretion.

Urate transport in the proximal tubule: in vivo and vesicle studies

1985 ◽  
Vol 249 (6) ◽  
pp. F789-F798 ◽  
Author(s):  
A. M. Kahn ◽  
E. J. Weinman
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Anion Exchanger ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Transport Processes ◽  
Basolateral Membrane Vesicles ◽  
Urate Transport ◽  
Rat Proximal Tubule

The transport of urate in the mammalian nephron is largely confined to the proximal tubule. Depending on the species, net reabsorption or net secretion is observed. The rat, like the human and the mongrel dog, demonstrates net reabsorption of urate and has been the most extensively studied species. The unidirectional reabsorption and secretion of urate in the rat proximal tubule occur via a passive and presumably paracellular route and by a mediated transcellular route. The reabsorption of urate, and possibly its secretion, can occur against an electrochemical gradient. A variety of drugs and other compounds affect the reabsorption and secretion of urate. The effects of these agents depend on their site of application (luminal or blood), concentration, and occasionally their participation in transport processes that do not have affinity for urate. Recent studies with renal brush border and basolateral membrane vesicles from the rat and brush border vesicles from the dog have determined the mechanisms for urate transport across the luminal and antiluminal membranes of the proximal tubule cell. Brush border membrane vesicles contain an anion exchanger with affinity for urate, hydroxyl ion, bicarbonate, chloride, lactate, p-aminohippurate (PAH), and a variety of other organic anions. Basolateral membrane vesicles contain an anion exchanger with affinity for urate and chloride but not for PAH. Both membrane vesicle preparations also permit urate translocation by simple diffusion. A model for the transcellular reabsorption and secretion of urate in the rat proximal tubule is proposed. This model is based on the vesicle studies, and it can potentially explain the majority of urate transport data obtained with in vivo techniques.

scholarly journals Differences in Ca2+-management between the ventricle of two species of neotropical teleosts: the jeju, Hoplerythrinus unitaeniatus (Spix & Agassiz, 1829), and the acara, Geophagus brasiliensis (Quoy & Gaimard, 1824)

2009 ◽  
Vol 7 (3) ◽  
pp. 471-478 ◽  
Author(s):  
Monica Jones Costa ◽  
Francisco Tadeu Rantin ◽  
Ana Lúcia Kalinin
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Physiological Role ◽  
Stimulation Frequency ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Heart Frequency ◽  
Geophagus Brasiliensis ◽  
Hoplerythrinus Unitaeniatus

This study analyzed the physiological role of the cardiac sarcoplasmic reticulum (SR) of two neotropical teleosts, the jeju, Hoplerythrinus unitaeniatus (Erythrinidae), and the acara, Geophagus brasiliensis (Cichlidae). While the in vivo heart frequency (fH - bpm) of acara (79.6 ± 6.6) was higher than that of the jeju (50.3 ± 2.7), the opposite was observed for the ventricular inotropism (Fc - mN/mm²) at 12 bpm (acara = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). A 5 min diastolic pause resulted in a strong potentiation of Fc (≅ 90%) of strips from jeju, which was completely abolished by ryanodine. Ryanodine also resulted in a ≅ 20% decrease in the Fc developed by strips from jeju at both subphysiological (12 bpm) and physiological (in vivo) frequencies. However, this effect of ryanodine reducing the Fc from jeju was completely compensated by adrenaline increments (10-9 and 10-6 M). In contrast, strips from acara were irresponsive to ryanodine, irrespective of the stimulation frequency, and increases in adrenaline concentration (to 10-9 and 10-6 M) further increased Fc. These results reinforce the hypothesis of the functionality of the SR as a common trait in neotropical ostariophysian (as jeju), while in acanthopterygians (as acara) it seems to be functional mainly in 'athletic' species.

scholarly journals Modified Sawhorse Waveform for the Voltammetric Detection of Oxytocin

2022 ◽  
Author(s):  
Favian Liu ◽  
Negar Ghasem Ardabili ◽  
Izaiah Brown ◽  
Harmain Rafi ◽  
Clarice Cook ◽  
...  
Keyword(s):  
Brain Slices ◽  
Physiological Role ◽  
Peptide Hormone ◽  
Protective Effects ◽  
Fast Scan Cyclic Voltammetry ◽  
The Past ◽  
Voltammetric Detection ◽  
Carbon Fiber Microelectrodes

Abstract Carbon fiber microelectrodes (CFMEs) have been used to detect neurotransmitters and other biomolecules using fast-scan cyclic voltammetry (FSCV) for the past few decades. This technique measures neurotransmitters such as dopamine and, more recently, physiologically relevant neuropeptides. Oxytocin, a pleiotropic peptide hormone, is physiologically important for adaptation, development, reproduction, and social behavior. This neuropeptide functions as a stress-coping molecule, an anti-inflammatory agent, and serves as an antioxidant with protective effects especially during adversity or trauma. Here, we measure tyrosine using the Modified Sawhorse Waveform (MSW), enabling enhanced electrode sensitivity for the amino acid and oxytocin peptide. Applying the MSW, decreased surface fouling and enabled codetection with other monoamines. As oxytocin contains tyrosine, the MSW was also used to detect oxytocin. The sensitivity of oxytocin detection was found to be 3.99 ± 0.49 nA/µM, (n=5). Additionally, we demonstrate that applying the MSW on CFMEs allows for real time measurements of exogenously applied oxytocin on rat brain slices. These studies may serve as novel assays for oxytocin detection in a fast, sub-second timescale with possible implications for in vivo measurements and further understanding of the physiological role of oxytocin.

scholarly journals Increased Fitness of Pseudomonas fluorescens Pf0-1 Leucine Auxotrophs in Soil

2008 ◽  
Vol 74 (12) ◽  
pp. 3644-3651 ◽  
Author(s):  
Wook Kim ◽  
Stuart B. Levy
Keyword(s):  
Pseudomonas Fluorescens ◽  
Bacterial Genome ◽  
Physiological Role ◽  
Underlying Mechanism ◽  
Growth Conditions ◽  
Soil Environment ◽  
Fitness Advantage ◽  
Gene Structures

ABSTRACT The annotation process of a newly sequenced bacterial genome is largely based on algorithms derived from databases of previously defined RNA and protein-encoding gene structures. This process generally excludes the possibility that the two strands of a given stretch of DNA can each harbor a gene in an overlapping manner. While the presence of such structures in eukaryotic genomes is considered to be relatively common, their counterparts in prokaryotic genomes are just beginning to be recognized. Application of an in vivo expression technology has previously identified 22 discrete genetic loci in Pseudomonas fluorescens Pf0-1 that were specifically activated in the soil environment, of which 10 were present in an antisense orientation relative to previously annotated genes. This observation led to the hypothesis that the physiological role of overlapping genetic structures may be relevant to growth conditions outside artificial laboratory media. Here, we examined the role of one of the overlapping gene pairs, iiv19 and leuA2, in soil. Although iiv19 was previously demonstrated to be preferentially activated in the soil environment, its absence did not alter the ability of P. fluorescens to colonize or survive in soil. Surprisingly, the absence of the leuA2 gene conferred a fitness advantage in the soil environment when leucine was supplied exogenously. This effect was determined to be independent of the iiv19 gene, and further analyses revealed that amino acid antagonism was the underlying mechanism behind the observed fitness advantage of the bacterium in soil. Our findings provide a potential mechanism for the frequent occurrence of auxotrophic mutants of Pseudomonas spp. in the lungs of cystic fibrosis patients.

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