Ability of sat-1 to transport sulfate, bicarbonate, or oxalate under physiological conditions

2009 ◽  
Vol 297 (1) ◽  
pp. F145-F154 ◽  
Author(s):  
Wolfgang Krick ◽  
Nina Schnedler ◽  
Gerhard Burckhardt ◽  
Birgitta C. Burckhardt
Keyword(s):  
Basolateral Membrane ◽  
Physiological Role ◽  
Experimental Conditions ◽  
Simultaneous Application ◽  
Proximal Tubule Cells ◽  
Sulfate Anion ◽  
Electrode Voltage ◽  
Electrophysiological Studies ◽  
Sat 1

Tubular reabsorption of sulfate is achieved by the sodium-dependent sulfate transporter, NaSi-1, located at the apical membrane, and the sulfate-anion exchanger, sat-1, located at the basolateral membrane. To delineate the physiological role of rat sat-1, [35S]sulfate and [14C]oxalate uptake into sat-1-expressing oocytes was determined under various experimental conditions. Influx of [35S]sulfate was inhibited by bicarbonate, thiosulfate, sulfite, and oxalate, but not by sulfamate and sulfide, in a competitive manner with Ki values of 2.7 ± 1.3 mM, 101.7 ± 9.7 μM, 53.8 ± 10.9 μM, and 63.5 ± 38.7 μM, respectively. Vice versa, [14C]oxalate uptake was inhibited by sulfate with a Ki of 85.9 ± 9.5 μM. The competitive type of inhibition indicates that these compounds are most likely substrates of sat-1. Physiological plasma bicarbonate concentrations (25 mM) reduced sulfate and oxalate uptake by more than 75%. Simultaneous application of sulfate, bicarbonate, and oxalate abolished sulfate as well as oxalate uptake. These data and electrophysiological studies using a two-electrode voltage-clamp device provide evidence that sat-1 preferentially works as an electroneutral sulfate-bicarbonate or oxalate-bicarbonate exchanger. In kidney proximal tubule cells, sat-1 likely completes sulfate reabsorption from the ultrafiltrate across the basolateral membrane in exchange for bicarbonate. In hepatocytes, oxalate extrusion is most probably mediated either by an exchange for sulfate or bicarbonate.

scholarly journals Oxalate: From the Environment to Kidney Stones

2013 ◽  
Vol 64 (4) ◽  
pp. 609-630 ◽  
Author(s):  
Hrvoje Brzica ◽  
Davorka Breljak ◽  
Birgitta C Burckhardt ◽  
Gerhard Burckhardt ◽  
Ivan Sabolić
Keyword(s):  
Underlying Mechanism ◽  
Stone Disease ◽  
Sulfate Anion ◽  
Intestinal Excretion ◽  
Oxalate Absorption ◽  
Anion Transporter ◽  
Solute Carrier ◽  
Sat 1 ◽  
Oxalate Transport

Abstract Oxalate urolithiasis (nephrolithiasis) is the most frequent type of kidney stone disease. Epidemiological research has shown that urolithiasis is approximately twice as common in men as in women, but the underlying mechanism of this sex-related prevalence is unclear. Oxalate in the organism partially originate from food (exogenous oxalate) and largely as a metabolic end-product from numerous precursors generated mainly in the liver (endogenous oxalate). Oxalate concentrations in plasma and urine can be modified by various foodstuffs, which can interact in positively or negatively by affecting oxalate absorption, excretion, and/or its metabolic pathways. Oxalate is mostly removed from blood by kidneys and partially via bile and intestinal excretion. In the kidneys, after reaching certain conditions, such as high tubular concentration and damaged integrity of the tubule epithelium, oxalate can precipitate and initiate the formation of stones. Recent studies have indicated the importance of the SoLute Carrier 26 (SLC26) family of membrane transporters for handling oxalate. Two members of this family [Sulfate Anion Transporter 1 (SAT-1; SLC26A1) and Chloride/Formate EXchanger (CFEX; SLC26A6)] may contribute to oxalate transport in the intestine, liver, and kidneys. Malfunction or absence of SAT-1 or CFEX has been associated with hyperoxaluria and urolithiasis. However, numerous questions regarding their roles in oxalate transport in the respective organs and male-prevalent urolithiasis, as well as the role of sex hormones in the expression of these transporters at the level of mRNA and protein, still remain to be answered.

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.

scholarly journals Involvement of Alternative Calcium Conductance on Human Myometrial Contractile and Pharmacological Properties

2018 ◽  
Vol 1 (1) ◽  
pp. 100-110
Author(s):  
Éric Rousseau ◽  
Karine Labelle ◽  
Laurence Massenavette
Keyword(s):  
Contractile Activity ◽  
Physiological Role ◽  
Rhythmic Activity ◽  
Isometric Tension ◽  
Human Myometrium ◽  
Trpc Channels ◽  
Tone Frequency ◽  
Experimental Conditions ◽  
Resting Tone

Objective: This study aimed to investigate the physiological role of alternative calcium conduct once contractions triggered by oxytocin and PGF? in human myometrium. This conductance, supported by TRPC and TRPV channels, may provide alternative pathways to control either free intracellular and/or submembrane Ca2+ - concentrations, which in turn will modulate membrane polarization and contractile responses. Study design: Uterine biopsies were obtained from consenting women undergoing elective caesarian delivery at term without labor (N = 29). Isometric tension measurements were performed on uterine strips (n = 174). Amplitudes, frequencies and areas under the curve (AUC) of phasic contractions as well as resting tone were measured under various experimental conditions. Norgestimate, which has been shown to inhibit TRPC isoforms, was added to isolated organ baths to delineate their putative functional involvement. In order to assess the role of TRPV4 channels, rhythmic activity triggered by uterotonic drugs was determined in the absence and presence of either 1 ?M HC-067047 (TRPV4 antagonist) or 100 nM GSK1016790A (TRPV4 agonist). Addition of 50 nM iberiotoxin (IbTX) as well as of 10 ?M NS-1619 was also used to assess the involvement of GKCa channels in controlling uterine reactivity and contractility.Results: Micromolar concentrations of norgestimate consistently decreased the resting tone, frequency and maximal amplitude of oxytocin - and PGF2? - induced contractions. In contrast, the TRPV4 agonist GSK1016790A abolished the rhythmic contractions, resulting in a strong and reversible tocolytic effect. Addition of iberiotoxin (a GKCa blocker) reversed the effects of GSK1016790A, while NS1619 mimicked the rapid tocolytic effects of the TRPV4 agonist. Conclusion: Acute pharmacological inhibition of TRPC channels by norgestimate had minor effects on contractile parameters although resting - tone was lowered. In contrast, selectiveTRPV4 activation led to GKCa activation, which in turn hyperpolarized the myometrial cell membrane, inactivating Ca2+ channels and efficiently abrogated contractile activity. Collectively, these data suggest that alternative calcium conduct ance may play a physiological role in the modulation of myometrial reactivity prior to delivery. A rapid switch from phasic contractions to quiescence by this new class of tocolytics may potentially be of interest in delaying parturition in preterm labor.

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.

Electrophysiological studies on primary cultures of proximal tubule cells

1986 ◽  
Vol 251 (3) ◽  
pp. F490-F498 ◽  
Author(s):  
E. Bello-Reuss ◽  
M. R. Weber
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Primary Cultures ◽  
Membrane Voltage ◽  
Collagen Membrane ◽  
Physiological Salt Solution ◽  
Proximal Tubule Cells ◽  
Electrophysiological Studies ◽  
Tubule Cells

Primary confluent monolayers were grown from proximal tubule fragments of rabbit kidneys. The fragments were obtained by gradient centrifugation and seeded on an ad hoc dish whose bottom was a permeable and transparent collagen membrane. The culture medium was a mixture of 50% Ham's F-12 and 50% Dulbecco's modified Eagle's medium supplemented with insulin, transferrin, ethanolamine, sodium selenite, and amino acids. The monolayers were studied at 6-14 days after seeding. Transmission electron microscopy revealed cuboidal cells 8.5-10.5 microns high, with a 1.5 to 2.5-microns apical brush border, abundant mitochondria, vacuoles, lysosomes, and irregular basal interdigitating processes. Cyclic AMP synthesis was stimulated by parathyroid hormone and was insensitive to vasopressin and isoproterenol. Electrophysiological studies performed with the same physiological salt solution on both sides revealed a transepithelial voltage of -2.6 +/- 0.6 mV (n = 10) and a basolateral membrane voltage of -51.0 +/- 4.5 mV (n = 13), both referred to the basal solution. The transepithelial electrical resistance was 7 +/- 2 omega X cm2. The apical membrane depolarized on addition of glucose to the apical side and hyperpolarized on removal of glucose. Changes in apical membrane voltage on addition of varying glucose concentrations (at [Na] = 135 mM, 37 degrees C) demonstrate the presence of a glucose transport system with an apparent Km of 3.54 +/- 0.54 and a Vmax of 7.2 +/- 0.4 mV. Thus this preparation exhibits morphological and electrophysiological characteristics of proximal tubule cells; these studies demonstrate the feasibility of the use of intracellular microelectrode techniques to study the transport properties of cultured epithelia.

Physiological role of glucocorticoids on rat serum and liver metallothionein in basal and stress conditions

1988 ◽  
Vol 254 (1) ◽  
pp. E71-E78
Author(s):  
J. Hidalgo ◽  
M. Giralt ◽  
J. S. Garvey ◽  
A. Armario
Keyword(s):  
Metal Binding ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Experimental Conditions ◽  
Rat Serum ◽  
Ru 486 ◽  
Positive Effect ◽  
Permissive Role

Serious contradictions exist at present in our understanding of the physiological role of glucocorticoids on the synthesis of the metal-binding protein, metallothionein (MT). In addressing this problem, we have examined in vivo the role of glucocorticoids on liver and serum MT levels in the rat under a spectrum of experimental conditions. The experiments confirm that stress has a major positive effect on hepatic MT levels. It was found that adrenocorticotropic hormone (ACTH) administration has an inhibitory effect on hepatic MT levels in response to restraint stress and that adrenalectomy (ADX) leads to an increase in basal MT levels and in MT levels in response to acute and chronic immobilization stress. Similar results followed treatment with the glucocorticoid receptor blocker, RU 486. The effect of ADX was abolished by corticosterone replacement. The relations found among hepatic MT, serum MT, and glucocorticoid concentrations indicate that in some circumstances glucocorticoids have a permissive role in mobilizing MT from tissues to serum and that in physiological conditions corticosterone has an inhibitory role in the maintenance of hepatic MT levels.

scholarly journals Properties of an Inwardly Rectifying ATP-sensitive K+ Channel in the Basolateral Membrane of Renal Proximal Tubule

1998 ◽  
Vol 111 (1) ◽  
pp. 139-160 ◽  
Author(s):  
Ulrich R. Mauerer ◽  
Emile L. Boulpaep ◽  
Alan S. Segal
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Physiological Role ◽  
K Channel ◽  
Nucleoside Triphosphate ◽  
Channel Activity ◽  
Open Probability ◽  
Proximal Tubule Cells ◽  
Tubule Cells

The potassium conductance of the basolateral membrane (BLM) of proximal tubule cells is a critical regulator of transport since it is the major determinant of the negative cell membrane potential and is necessary for pump-leak coupling to the Na+,K+-ATPase pump. Despite this pivotal physiological role, the properties of this conductance have been incompletely characterized, in part due to difficulty gaining access to the BLM. We have investigated the properties of this BLM K+ conductance in dissociated, polarized Ambystoma proximal tubule cells. Nearly all seals made on Ambystoma cells contained inward rectifier K+ channels (γslope, in = 24.5 ± 0.6 pS, γchord, out = 3.7 ± 0.4 pS). The rectification is mediated in part by internal Mg2+. The open probability of the channel increases modestly with hyperpolarization. The inward conducting properties are described by a saturating binding–unbinding model. The channel conducts Tl+ and K+, but there is no significant conductance for Na+, Rb+, Cs+, Li+, NH4+, or Cl−. The channel is inhibited by barium and the sulfonylurea agent glibenclamide, but not by tetraethylammonium. Channel rundown typically occurs in the absence of ATP, but cytosolic addition of 0.2 mM ATP (or any hydrolyzable nucleoside triphosphate) sustains channel activity indefinitely. Phosphorylation processes alone fail to sustain channel activity. Higher doses of ATP (or other nucleoside triphosphates) reversibly inhibit the channel. The K+ channel opener diazoxide opens the channel in the presence of 0.2 mM ATP, but does not alleviate the inhibition of millimolar doses of ATP. We conclude that this K+ channel is the major ATP-sensitive basolateral K+ conductance in the proximal tubule.

scholarly journals Role of a tyrosine kinase in the CO2-induced stimulation of HCO3− reabsorption by rabbit S2 proximal tubules

2006 ◽  
Vol 291 (2) ◽  
pp. F358-F367 ◽  
Author(s):  
Yuehan Zhou ◽  
Patrice Bouyer ◽  
Walter F. Boron
Keyword(s):  
Tyrosine Kinase ◽  
Egf Receptor ◽  
Kinase Inhibitor ◽  
Basolateral Membrane ◽  
Proximal Tubule Cells ◽  
High Affinity ◽  
Egf Receptor Family ◽  
Acute Changes ◽  
Receptor Family

A previous study demonstrated that proximal tubule cells regulate HCO3− reabsorption by sensing acute changes in basolateral CO2 concentration, suggesting that there is some sort of CO2 sensor at or near the basolateral membrane (Zhou Y, Zhao J, Bouyer P, and Boron WF Proc Natl Acad Sci USA 102: 3875–3880, 2005). Here, we hypothesized that an early element in the CO2 signal-transduction cascade might be either a receptor tyrosine kinase (RTK) or a receptor-associated (or soluble) tyrosine kinase (sTK). In our experiments, we found, first, that basolateral 17.5 μM genistein, a broad-spectrum tyrosine kinase inhibitor, virtually eliminates the CO2 sensitivity of HCO3− absorption rate ( J[Formula: see text]). Second, we found that neither basolateral 250 nM nor basolateral 2 μM PP2, a high-affinity inhibitor for the Src family that also inhibits the Bcr-Abl sTK as well as the Kit RTK, reduces the CO2-stimulated increase in J[Formula: see text]. Third, we found that either basolateral 35 nM PD168393, a high-affinity inhibitor of RTKs in the erbB (i.e., EGF receptor) family, or basolateral 10 nM BPIQ-I, which blocks erbB RTKs by competing with ATP, eliminates the CO2 sensitivity. In conclusion, the transduction of the CO2 signal requires activation of a tyrosine kinase, perhaps an erbB. The possibilities include the following: 1) a TK is simply permissive for the effect of CO2 on J[Formula: see text]; 2) a CO2 receptor activates an sTK, which would then raise J[Formula: see text]; 3) a CO2 receptor transactivates an RTK; and 4) the CO2 receptor could itself be an RTK.

scholarly journals Redox artifacts in electrophysiological recordings

2013 ◽  
Vol 304 (7) ◽  
pp. C604-C613 ◽  
Author(s):  
Jonathan M. Berman ◽  
Mouhamed S. Awayda
Keyword(s):  
Voltage Clamp ◽  
Membrane Conductance ◽  
Chloride Ions ◽  
Experimental Conditions ◽  
Chemical Reagents ◽  
Electrophysiological Recordings ◽  
Electrode Voltage ◽  
Electrophysiological Studies ◽  
Increased Sensitivity ◽  
Chloride Deposition

Electrophysiological techniques make use of Ag/AgCl electrodes that are in direct contact with cells or bath. In the bath, electrodes are exposed to numerous experimental conditions and chemical reagents that can modify electrode voltage. We examined voltage offsets created in Ag/AgCl electrodes by exposure to redox reagents used in electrophysiological studies. Voltage offsets were measured in reference to an electrode separated from the solution by an agar bridge. The reducing reagents Tris-2-carboxyethly-phosphine, dithiothreitol (DTT), and glutathione, as well as the oxidizing agent H2O2used at experimentally relevant concentrations reacted with Ag in the electrodes to produce voltage offsets. Chloride ions and strong acids and bases produced offsets at millimolar concentrations. Electrolytic depletion of the AgCl layer, to replicate voltage clamp and sustained use, resulted in increased sensitivity to flow and DTT. Offsets were sensitive to electrode silver purity and to the amount and method of chloride deposition. For example, exposure to 10 μM DTT produced a voltage offset between 10 and 284 mV depending on the chloride deposition method. Currents generated by these offsets are significant and dependent on membrane conductance and by extension the expression of ion channels and may therefore appear to be biological in origin. These data demonstrate a new source of artifacts in electrophysiological recordings that can affect measurements obtained from a variety of experimental techniques from patch clamp to two-electrode voltage clamp.

scholarly journals Metabolic Engineering of Acetaldehyde Production by Streptococcus thermophilus

2002 ◽  
Vol 68 (11) ◽  
pp. 5656-5662 ◽  
Author(s):  
A. C. S. D. Chaves ◽  
M. Fernandez ◽  
A. L. S. Lerayer ◽  
I. Mierau ◽  
M. Kleerebezem ◽  
...  
Keyword(s):  
Starter Culture ◽  
Physiological Role ◽  
Streptococcus Thermophilus ◽  
Experimental Conditions ◽  
Severe Reduction ◽  
Main Pathway ◽  
Fermented Dairy Products ◽  
Fermented Dairy ◽  
Acetaldehyde Production

ABSTRACT The process of acetaldehyde formation by the yogurt bacterium Streptococcus thermophilus is described in this paper. Attention was focused on one specific reaction for acetaldehyde formation catalyzed by serine hydroxymethyltransferase (SHMT), encoded by the glyA gene. In S. thermophilus, SHMT also possesses threonine aldolase (TA) activity, the interconversion of threonine into glycine and acetaldehyde. In this work, several wild-type S. thermophilus strains were screened for acetaldehyde production in the presence and absence of l-threonine. Supplementation of the growth medium with l-threonine led to an increase in acetaldehyde production. Furthermore, acetaldehyde formation during fermentation could be correlated to the TA activity of SHMT. To study the physiological role of SHMT, a glyA mutant was constructed by gene disruption. Inactivation of glyA resulted in a severe reduction in TA activity and complete loss of acetaldehyde formation during fermentation. Subsequently, an S. thermophilus strain was constructed in which the glyA gene was cloned under the control of a strong promoter (PLacA). When this strain was used for fermentation, an increase in TA activity and in acetaldehyde and folic acid production was observed. These results show that, in S. thermophilus, SHMT, displaying TA activity, constitutes the main pathway for acetaldehyde formation under our experimental conditions. These findings can be used to control and improve acetaldehyde production in fermented (dairy) products with S. thermophilus as starter culture.

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