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At least 1,423 records · Page 79Linked to original sources
PubMed2006

First hyperpolarizabilities of 1,3,5-tricyanobenzene derivatives: origin of larger beta values for the octupoles than for the dipoles.

A series of donor-acceptor substituted stilbene and diphenylacetylene derivatives and their octupolar analogues have been synthesized and the linear and nonlinear optical properties (beta) studied by both experiments and theoretical calculation. The lambda(max) of the dipoles increases with the conjugation length and is always larger when the C=C bond is used, instead of the C[triple bond]C bond, as the conjugation bridge. Although the lambda(max) values of the octupoles show no clear trend, they are much larger than those of the dipoles. The beta(0) values of the dipoles increase with conjugation length and as the conjugation bridge is changed from the C[triple bond]C to C=C bond. This increase is accompanied by an increase in either lambda(max) or the oscillator strength. Similarly, the beta(0) values of the octupoles increase with the conjugation length and with a change in the donor in the order: NEt2 < N(i-amyl)Ph < NPh2. Moreover, beta(yyy)/beta(zzz) ratios are in the range of 1.6-3.9 and decrease with the conjugation length. Beta values calculated by the finite-field and sum-over-states methods are in good agreement with the experimental data. Also, there is a parallel relationship between the calculated beta values and bond length alternation (BLA). From these results, the origin of the larger beta values for octupoles than for dipoles is assessed.

Journal Article↗
PubMed2004

Separation of flavonoids and phenolic acids from propolis by capillary zone electrophoresis.

The simultaneous determination of twelve different flavonoids, pinocembrin, acacetin, chrysin, rutin, catechin, naringenin, galangin, luteolin, kaempferol, apigenin, myricetin, and quercetin, two phenolic acids, cinnamic acid and caffeic acid, and one stilbene derivative, resveratrol, in propolis extracts used in medicine has been investigated by capillary zone electrophoresis (CZE). With a buffer constituted by sodium tetraborate 30 mM, pH 9.0, and 15 kV applied voltage, the 15 polyphenols were separated on an uncoated fused-silica capillary within 40 min using normal polarity. Under the experimental conditions used, a linear relationship was calculated between the CZE migration times and the molecular weight of polyphenols' expression of the increasing amount of their hydroxyl groups and polarity. Regression equations revealed a linear relationship (correlation coefficients > 0.97) between the peak area of each polyphenol species and their concentration, from 6 to 120 ng. The levels of analytes in three different propolis extracts, ethanolic, aqueous-ethanolic and aqueous-glycolic, used to prepare various commercial medicinal products, were determined. The aqueous-ethanolic propolis extract showed a great percentage of caffeic acid, galangin, quercetin, and chrysin, whilst the ethanolic preparation was composed of a great amount of resveratrol, chrysin, and caffeic acid. On the contrary, the aqueous-glycolic propolis preparation was composed of approx. 11% of caffeic acid and a low amount of the other identified flavonoids due to the presence of approx. 85% of nonidentified compounds. CZE represents a valuable method for the qualitative and quantitative assay of the most relevant polyphenol components of propolis, representing an alternative to obtain typical fingerprints of propolis and a reliable identification of a large number of propolis polyphenolic species.

Electrophoresis, Capillary↗
PubMed2005

ATP binding cassette transporter ABC1 is required for the release of interleukin-1beta by P2X7-stimulated and lipopolysaccharide-primed mouse Schwann cells.

Schwann cells are best known as myelinating glial cells of the peripheral nervous system, but they also participate actively in the sphere of immunity by producing pro-inflammatory cytokines, such as interleukin-1beta (IL-1beta). In a previous study, we demonstrated that posttranslational processing of IL-1beta by immune-challenged Schwann cells required the P2X7 receptor. Remarkably, the release of IL-1beta was not associated with cell death, indicating the involvement of an active mechanism. ATP binding cassette (ABC) transporters are known to transport leaderless secretory proteins, such as IL-1beta; therefore, we investigated whether such transporters were at work in Schwann cells. Mouse Schwann cells expressed ABC1 transporter mRNA and displayed the functional protein. Glybenclamide and diisothiocyanato-stilbene-disulfonic acid (DIDS), two blockers of chloride fluxes that drive the export activity of ABC1 transporters, inhibited IL-1beta release without altering its intracellular processing. Enhancing chloride efflux potentiated the release of IL-1beta, while decreasing it led to a strong reduction in its release. Because the stimulation of the P2X7 receptor also activates a chloride conductance, we investigated the possibility of a sole anionic pathway mobilized by the P2X7 receptor and ABC1. Glybenclamide and DIDS had no significant effects on the P2X7-activated chloride current suggesting therefore the existence of two different pathways. In summary, ABC1 transporters are required for the release of IL-1beta by mouse Schwann cells. Being associated together with chloride conductance, P2X7 receptors and ABC1 transporters delineate a subtle and complex regulation of IL-1beta production in mammalian Schwann cells. Furthermore, ABC1 transporters could be a target of therapeutic interest for regulating IL-1beta activity in neuroinflammation disorders.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1988

Electrogenic Na+/HCO3- cotransport in neuroglia.

Membrane potential recording from glial cells in Necturus optic nerve in the presence of 2 mM Ba++, which was added to block the K+ conductance, gave the following results. 1) In HCO3- -free, low-Na+ solutions (11% of control; Na+ replaced with N-methyl-D-glucamine), the hyperpolarizing effect of adding 10 mM HCO3- was reduced by approximately 80%. 2) 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS, 0.1 or 1 mM) reduced the effect of HCO3- by at least 50%. 3) In the presence of HCO3-, reduction of Na+ caused a depolarization which was much larger than that observed in nominally HCO3- -free solutions. These observations indicate the presence in the glial membrane of an electrogenic Na+/HCO3- cotransporter in which the stoichiometry of HCO3- to Na+ is greater than 1.

Animals↗
PubMed1993

Single ion channel currents in neuropile glial cells of the leech central nervous system.

The patch-clamp technique was used to investigate the activity of single ion channels in neuropile glial (NG) cells in the central nervous system (CNS) of the medicinal leech, Hirudo medicinalis. We found evidence for two distinct Cl- channels that could be distinguished by their basic electrical properties and their responses to different inhibitors on single ion channel currents. In the inside-out configuration in symmetrical Cl- solutions, these channels showed current-voltage relationships with slight outward rectification, mean conductances of 70 and 80 pS, and reversal potentials near 0 mV. Significant permeability to Na+, K+, or SO4(2-) could not be detected. The open-state probability of the 70 pS Cl- channel increased with membrane depolarization, whereas the open-state probability of the 80 pS Cl- channel was voltage-independent. The application of the stilbene derivative DIDS (100 microM) to the cytoplasmic side of the glial cell membrane blocked both Cl- channels. The activity of the 70 pS channel was blocked irreversibly by DIDS, whereas the activity of the 80 pS channel reappeared after wash-out of DIDS. Both channels were blocked reversibly by 1 mM Zn2+. K+ channels could only be observed occasionally in the soma membrane of the NG cells. We have characterized a 60 pS K+ channel with a high selectivity for K+ over Na+. The low density of K+ channels in the soma membrane may indicate a non-uniform distribution of this channel type in NG cells.

Action Potentials↗
PubMedDate not supplied

Evidence for a channel for the electrogenic transport of chloride ion in the rat hepatocyte.

Chloride is the major inorganic anion in bile but its mechanism of passage from blood to bile is uncertain. Specific membrane channels account for most net inorganic anion flux in other cell types such as the proximal tubular cell and red blood cell; disulfonic stilbenes inhibit anion movement through these channels. Therefore, we have sought the presence of similar channels in the hepatocyte. Net inorganic anion flux or conductance was initiated in isolated rat hepatocytes by valinomycin in the presence of an outward potassium gradient. Potassium concentration in the extracellular medium increased from 2.75 +/- 0.02 in control cell suspensions to 3.15 +/- 0.04 in valinomycin-treated cell suspensions. Membrane potential difference (Em) (mV), determined as the distribution of [14C]tetraphenyl phosphonium ion was -28 mV in control cells and -42 mV in valinomycin-treated cells (p less than 0.05). Intracellular chloride concentration (36Cl-) (mEq per liter of cell water) decreased significantly from 38.6 in control cells to 32.0 in valinomycin-treated cells. The observed intracellular concentrations (36Cl-) in both control and valinomycin-treated cell suspensions closely approximates values predicted on the basis of the Nernst equation: 41 and 29 (mEq per liter of cell water), respectively, suggesting that the chloride ion is passively distributed on the basis of the membrane potential difference. Furthermore, net rate-limited cell water loss of approximately 15% of control values was associated with the above valinomycin-stimulated changes in ion distribution, as assessed using three methods of cell water volume determination.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1992

Characterization of the transport of a synthetic bile salt, iodinated cholyl-glycyl-tyrosine, in isolated cultured rat hepatocytes.

The uptake of tri-hydroxy conjugated bile salts by hepatocytes is principally by a sodium-dependent carrier. We examined the uptake kinetics of the high-specific-activity, hydroxylated, conjugated bile salt 125I-labeled cholyl-glycyl-tyrosine, to determine whether this synthetic bile salt was transported by the sodium-dependent bile salt system. 125I-labeled cholyl-glycyl-tyrosine was synthesized, and its transport kinetics were studied in freshly cultured rat hepatocytes. Uptake into hepatocytes was time and temperature dependent and was decreased by the inhibitors diisothiocyanodisulfonic acid stilbene, probenecid and carbonyl cyanide chlorophenyl hydrazone, demonstrating carrier mediation and energy dependence. At concentrations of iodinated cholyl-glycyl-tyrosine less than 10 mumol/L, uptake was 27% +/- 5% sodium dependent, whereas at concentrations from 10 mumol/L to 40 mumol/L uptake was 52% +/- 4% sodium dependent. The apparent affinity for uptake of 125I-labeled cholyl-glycyl-tyrosine was 8 +/- 2 mumol/L, and the maximal velocity was 50 +/- 20 pmol/micrograms DNA/min. Both taurocholate and indocyanine green inhibited uptake of 125I-labeled cholyl-glycyl-tyrosine. Indocyanine green inhibited the uptake of 125I-labeled cholyl-glycyl-tyrosine (Ki = 10 microns) more effectively than taurocholate (Ki = 20 microns). We conclude that 125I-labeled cholyl-glycyl-tyrosine is not a specific probe for either sodium-dependent bile salt or sodium-independent organic anion carriers, but appears to use both systems in a concentration-dependent manner in cultured rat hepatocytes.

Animals↗
PubMed1985

Mediation of anion transport in oocytes of Xenopus laevis by biosynthetically inserted band 3 protein from mouse spleen erythroid cells.

mRNA from the spleens of anemic mice was purified by oligo(dT)-cellulose chromatography and fractionated by density gradient centrifugation. After injection into oocytes of Xenopus laevis, two of the four fractions obtained led, after 16 h of incubation at 20 degrees C, to the expression of mouse band 3 protein, as demonstrated by immunoprecipitation with polyclonal antibodies against mouse band 3. Flux measurements showed an approximately 2- to 4-fold increment of 36Cl- uptake, which could be abolished by two different stilbene disulfonates, specific inhibitors of band 3-mediated anion transport in red blood cells.

Animals↗
PubMed1988

Characterization of an anion-permeable channel from sugar beet vacuoles: effect of inhibitors.

The vacuole occupies 25-95% of the plant cell volume and plays an essential role in maintaining cytoplasmic homeostasis of nutrients and ions. Recent patch-clamp studies identified ion channels and electrogenic pumps as pathways for the movement of ions and metabolites across the vacuolar membrane (tonoplast). At high cytoplasmic Ca (>10 M) and negative potentials (inside the vacuole) non-selective channels of the ;slow-vacuolar (SV)-type' were activated resulting in anion release or cation influx. In the present study these vacuolar channels were characterized pharmacologically by ion channel inhibitors. The cation-transport inhibitors Ba, TEA and amiloride caused only partial and reversible block of the ;SV-type'channels, whereas anion-transport inhibitors strongly affected the vacuolar channels. Pyridoxalphosphate and the dimethylaminecarboxylate derivates anthracene-9-carboxylic acid and C 144 reversibly blocked the channels up to 70% and Zncl(2) up to 95%. DIDS and SITS inhibited this channel irreversibly up to 95%. The block developed under a variety of experimental conditions using solutions containing combinations of permanent cations and anions. The DIDS binding site is located on the cytoplasmic surface of the tonoplast, as intravacuolar DIDS did not block the channels. DIDS concentrations in the micromolar range, efficient in blocking 70-80% of the ;SV-type' channels did not significantly affect ATP-induced or pyrophosphate-induced proton-pumps. Stilbene derivatives may therefore be useful tools for studies on the substrate binding site on this vacuolar channel and for channel isolation.

Journal Article↗
PubMed1993

An ATP transporter is required for protein translocation into the yeast endoplasmic reticulum.

The transfer of precursor proteins through the membrane of the rough endoplasmic reticulum (ER) in yeast is strictly dependent on the presence of ATP. Since Kar2p (the yeast homologue of mammalian BiP) is required for translocation, and is an ATP binding protein, an ATP transport system must be coupled to the translocation machinery of the ER. We report here the characterization of a transport system for ATP in vesicles derived from yeast ER. ATP uptake into vesicles was found to be saturable in the micromolar range with a Km of 1 x 10(-5) M. ATP transport into ER vesicles was specifically inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), a stilbene derivative known to inhibit a number of other anion transporters, and by 3'-O-(4-benzoyl)benzoyl-ATP (Bz2-ATP). Inhibition of ATP uptake into yeast microsomes by DIDS and Bz2-ATP blocked protein translocation in vitro measured co- as well as post-translationally. The inhibitory effect of DIDS on translocation was prevented by coincubation with ATP. Moreover, selective membrane permeabilization, allowing ATP access to the lumen, restored translocation activity to DIDS-treated membranes. These results demonstrate that translocation requires a DIDS and Bz2-ATP-sensitive component whose function is to transport ATP to the lumen of the ER. These findings are consistent with current models of protein translocation in yeast which stipulate the participation of Kar2p in the translocation process.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1985

The mechanisms of action of cyanide on the rabbit aorta.

Pretreatment of strips of rabbit aorta with 10(-3) M sodium cyanide reduced contractions to 10(-8) through 10(-4) M norepinephrine (NE) added cumulatively. This antagonism by cyanide was not altered by 4 X 10(-6) M ouabain or verapamil, suggesting a lack of involvement of Na+, K+ ATPase or of calcium influx in the antagonism. Cyanide potentiated contractions caused by 3 X 10(-2) M potassium, but reduced contractions induced by higher potassium concentrations. Because the antagonism of higher concentrations of potassium and NE were similar, it seems that selective actions on different calcium pools are possibly not involved in the antagonism of agonist-induced contractions. 10(-2) M cyanide contracted rabbit aorta with a mean contraction 16% of that induced by 10(-4) M NE. These contractions were potentiated by pretreatment with 4 X 10(-6) M ouabain and 4 X 10(-6) M verapamil but were unaffected by the serotonin antagonist 2-bromo lysergic acid diethylamide, 10(-4) M (2-BrLSD), the alpha adrenergic antagonist phentolamine, 4 X 10(-5) M, the H1 antihistaminic pyrilamine, 10(-5) M, or the antimuscarinic atropine, 10(-6) M. The contractions were reduced by 10(-4) M 4,4'-di-isothiocyano-2,2'-stilbene disulfonic acid (DIDS) or chlorpromazine. The reduction may be due to a blockade of anionic channel mechanisms facilitating entry of cyanide into the vascular smooth muscle cell, as both of these agents can block anionic channels in other tissues.

Animals↗
PubMed1990

Biochemical characterization of an electrogenic vacuolar proton pump in purified chicken osteoclast plasma membrane vesicles.

A well-characterized chicken osteoclast plasma membrane vesicle preparation manifested Mg2(+)-dependent ATP hydrolyzing activity of 0.213 mumol inorganic phosphate released per mg protein per minute (n = 7). The Mg2+ dependence showed a high-affinity component with a KMg of 1.293 microM and Vmax of 0.063 mumol Pi per mg protein per minute, and a low-affinity component with a KMg of 297.6 microM and a Vmax of 0.232 mumol Pi per mg protein per minute. The Mg2(+)-ATPase activity was inhibited by N,N'-dicyclohexylcarbodiimide (DCCD, 0.2 mM, 50.7%), N-ethylmaleimide (0.5 mM, 34.6%), nolinium bromide (1 mM, 29.9%), 4,4'-diisothiocyano-2,2'-stilbene sulfonic acid (DIDS, 1 mM, 45.1%), and p-chloromercuribenzoic acid (PCMB, 0.1 mM, 33.8%). Sodium orthovanadate (Na3 VO4) at 1 microM had no effect but caused 29.5% inhibition at 1 mM. Na+ could substitute for K+ without loss of activity, NO3- caused 19.5% inhibition when substituted for Cl-, and acetate replacement of Cl- resulted in 36.4% stimulation of Mg2(+)-ATPase. ATP, GTP, ITP, CTP, and ADP were all hydrolyzed effectively. DCCD (0.2 mM), NEM (0.5 mM), nolinium bromide (1 mM), and DIDS (50 microM) almost completely abolished proton transport as measured spectrofluorometrically by acridine orange quenching. Na3 VO4 (1 mM) had no effect, and duramycin (80 micrograms/ml) inhibited transport 52.7%. K+ replacement of Na+ caused a 79.2% increase in initial proton transport rate. NO3- and acetate substitution of Cl- resulted in a 46.1 and 55.7% decrease in transport, respectively. ATP supports transport far more effectively than the other nucleotides tested. ADP was ineffective. Experiments using the potassium ionophore, valinomycin, indicated that the proton pump functions electrogenically, with Cl- most likely cotransported by an anion transporter. The proton pump also seems to have at least one anion-sensitive site, elucidated by experiments in the presence of NO3- and Cl-.

Animals↗
PubMed1986

Immunochemical characterization of human lung epoxide hydrolases.

Immunochemical techniques were used to investigate the biochemical properties of human lung epoxide hydrolases. Two epoxide hydrolases with different immunoreactive properties were identified. These two epoxide hydrolases were found in both cytosolic and microsomal cell fractions. Immunotitration of enzyme activity showed that enzymes that catalyze the hydration of benzo(a)pyrene 4,5-oxide react with antiserum to rat microsomal epoxide hydrolase; those that hydrate trans-stilbene oxide do not. Immunotitration and Western blot experiments showed that microsomal and cytosolic benzo(a)pyrene 4,5-oxide hydrolases have significant structural homology. Immunohistochemical staining of human lung benzo(a)pyrene 4,5-oxide hydrolase showed that the enzyme is localized primarily in the bronchial epithelium. No cell type-specific localization was observed. An enzyme-linked immunosorbent assay was developed which allows direct quantitation of benzo(a)pyrene 4,5-oxide hydrolase protein. Levels of enzyme protein detected by this assay correlated well with enzyme levels determined by substrate conversion assays.

Animals↗
PubMed1989

Selective inhibition of cytosolic epoxide hydrolase activity in vitro by compounds that inhibit catalase.

The ability of a number of known inhibitors of catalase activity to affect cytosolic and microsomal epoxide hydrolase activities in vitro, measured as enzymatic trans-stilbene oxide hydrolysis and styrene oxide hydrolysis, respectively, was investigated. Catalase and cytosolic epoxide hydrolase activities are inhibited by hydroxylated metabolites of 2-amino-4,5-diphenylthiazole (DPT). The metabolite hydroxylated on the 4-phenyl ring (4OH-DPT) and the metabolite hydroxylated on both phenyl rings (4,5-DIOH-DPT) are potent inhibitors of both enzymes; the metabolite hydroxylated on the 5-phenyl ring (5OH-DPT) is less potent. Unmetabolized DPT has no effect on either enzyme. 4OH-DPT inhibits, but 5OH-DPT enhances, microsomal epoxide hydrolase activity. 4,5-DIOH-DPT and DPT have no effect on this enzyme. Other compounds that inhibit both catalase and cytosolic epoxide hydrolase activities, but do not inhibit microsomal epoxide hydrolase activity, are nordihydroguaiaretic acid and 2-aminothiazole. Microsomal epoxide hydrolase activity is enhanced by 2-aminothiazole and levamisole in vitro. Thus these inhibitors of catalase are selective epoxide hydrolase inhibitors in that they inhibit cytosolic epoxide hydrolase activity in vitro, but have either no effect on, or increase the activity of, microsomal epoxide hydrolase in vitro. Conversely, the selective cytosolic epoxide hydrolase inhibitors 4-phenylchalcone oxide and 4'-phenylchalcone oxide do not inhibit catalase activity, nor does trichloropropene oxide, a selective microsomal epoxide hydrolase inhibitor.

Animals↗
PubMed1990

Multiple pathways for the oxidative metabolism of estrogens in Syrian hamster and rabbit kidney.

Microsomal preparations from hamster kidney, a target tissue for the carcinogenic action of stilbene-type and steroidal estrogens, catalyze the oxidative metabolism of diethylstilbestrol (DES). The formation of the major metabolite Z,Z-dienestrol and of reactive intermediates capable of protein binding were mediated by enzyme activities requiring nicotinamide-adenine dinucleotide phosphate (reduced form-NADPH), cumene hydroperoxide, or arachidonic acid (ARA). In addition, hydroxylated DES metabolites were detected in NADPH-supplemented incubations. The NADPH-dependent oxidation of DES was inhibited by SKF 525A and metyrapone. Monooxygenase-catalyzed metabolism was apparently responsible for the majority of DES oxidation in microsomes from whole hamster kidneys in vitro and this activity is preferentially localized in the kidney cortex. However, ARA-dependent, i.e., prostaglandin H synthase (PHS) mediated oxidation of DES and of the catechol estrogen 2-hydroxyestrone was demonstrated as well in the medulla of both rabbit and hamster kidney. It is proposed that monooxygenase and PHS activities act in concert in the metabolic activation of carcinogenic estrogens. This appears to apply in particular to steroidal estrogens, since catechol estrogens formed by monooxygenases are further oxidized to reactive intermediates by PHS and other peroxidatic enzymes.

Animals↗
PubMed2003

Theoretical study of the internal elimination reactions of xanthate precursors.

The gas-phase internal elimination (E(i)) reaction of ethyl xanthate (CH(3)-CH(2)-S-CS-O-CH(3)) has been investigated by means of Hartree-Fock, second-order Møller-Plesset, and density functional theory (DFT) using the Becke three-parameter Lee-Yang-Parr (B3LYP) functional and the modified Perdew-Wang one-parameter model for kinetics (MPW1K). Considerable differences between the ground- and transition-state geometries and the calculated activation energies are observed from one approach to the other, which justifies first a careful calibration of the methods against the results of benchmark CCSD(T) calculations. Compared with these, DFT calculations along with the MPW1K functional are found to be an appropriate choice for describing the E(i) reaction of xanthate precursors. The precursor conformation and the transition states involved in the internal conversion of xanthate precursors of cyano derivatives of ethylene, and of cis- and trans-stilbene, are then characterized in detail by means of this functional.

Journal Article↗
PubMed1984

Anion requirement and effect of anion transport inhibitors on the response of vero cells to diphtheria toxin and modeccin.

The anion requirement for toxic action of diphtheria toxin and modeccin was studied. In Cl- -free Hepes buffer made isotonic with mannitol, cells were insensitive to diphtheria toxin and modeccin. Just 2 mM NaCl was sufficient to obtain full toxic activity of modeccin, whereas 140 mM NaCl was required for maximal intoxication with diphtheria toxin. Br- could substitute for Cl-. NO3-,l-, and ClO3- were less efficient than Cl-, whereas SO42- and SCN- were unable to replace Cl- . Cl- deprivation both reduced the ability of cells to bind diphtheria toxin and prevented bound toxin from intoxicating the cells. The binding of modeccin was not reduced. SITS (4-acetamide-4'-isothiocyano-stilbene-2,2'-disulfonic acid), an inhibitor of Cl- entry, protected against diphtheria toxin and modeccin, indicating that Cl- transport is required for intoxication.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1984

Characterization of monovalent ion transport systems in an insect cell line (Manduca sexta embryonic cell line CHE).

The monovalent ion transport systems of an immortalized insect cell line (CHE) have been investigated. These cells are unusual in that unlike most vertebrate cells, their normal extracellular environment consists of high potassium and low sodium concentrations. CHE cells maintained high intracellular [K+] through both a furosemide-inhibitable and a vanadate-inhibitable transport system. Intracellular exchangeable [Na+] was slightly lower than the extracellular [Na+] and was maintained at this level through a vanadate-sensitive transport system. Na+ uptake was also inhibited by furosemide: however, the stoichiometry of furosemide-sensitive Na+ uptake when compared with furosemide-sensitive K+ uptake indicated that these cations are not cotransported. 4,4'-Diisothiocyano-2,2'-disulfonic acid stilbene (DIDS) inhibited Na+, K+, and Cl- uptake. Vanadate and furosemide decreased cytoplasmimic pH, while cytoplasmic pH increased in the presence of DIDS. A model is presented explaining how Na+, K+, Cl-, H+ and HCO3-fluxes are regulated in these cells.

Animals↗