Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Flufenamic Acid”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1985

Solute-induced acceleration of transbilayer movement and its implications on models of blood-brain barrier.

Hexylglycerol accelerates the transbilayer (flip-flop) movement of phospholipids, lysophospholipids and peptides. For example, lysophosphatidylcholine added to dimyristoylphosphatidylcholine vesicles activates the action of pig pancreatic phospholipase A2 (Jain and DeHaas (1983) Biochim. Biophys. Acta 736, 157-162) This activating effect is dissipated slowly after mixing, and no activation is observed when the lysophospholipid molecules are equally distributed on both sides of the bilayer. The half time for transbilayer movement of lysophosphatidylcholine is about 7 h, and it is accelerated over 100-fold in the presence of n-hexylglycerol, as well as by a variety of other amphipathic solutes including n-alkanols, ketamine, and flufenamic acid. Hexylglycerol also accelerates the rate of transbilayer movement of an amphipathic hexapeptide bocLALALW, as well as of the phosphatidylcholine molecules in erythrocyte membrane. These effects are observed without any change in the gross bilayer organization as judged by 31P-NMR. Biophysical significance of such solute induced acceleration of transbilayer movement of amphipathic solutes is discussed to account for the effect of alkylglycerols on blood brain barrier.

Animals↗
PubMed1980

Surfactant secretion in a newborn rabbit lung slice model.

We describe a slice model for the study of pulmonary surfactant secretion in newborn rabbits. Full term rabbits were delivered by cesarean section and injected intraperitoneally with [Me-3H]choline. Four hours later they were killed, the lungs were perfused to remove blood, slices (0.5 mm thick) were prepared and incubated in buffer at 37 degrees C. The composition of the lipids initially released into the medium resembled those of lung tissue rather than surfactant. Following 3 changes of medium, however, the composition of the lipids released was very similar to that of lung lavage. Phosphatidylcholine accounted for over 70% of the total while phosphatidylethanolamine and sphingomyelin accounted for only 7% and 4%, respectively. 52% of the phosphatidylcholine was disaturated. Less than 5% of the tissue lactate dehydrogenase was released into the medium. The rate of phosphatidyl[Me-3H]choline release during this period was, therefore, measured. Release of phosphatidyl[Me-3H]choline was linear with time and was temperature-dependent. Prostaglandin E2 stimulated its rate of release by 20% while indomethacin and flufenamic acid, inhibitors of prostaglandin synthesis, inhibited it by 52% and 37%, respectively. The calcium ionophore A23187 in the presence of Ca2+ stimulated release by 40% while colchicine an cytochalasin B inhibited it by 36% and 32%, respectively. These data suggest that both prostaglandins and Ca2+ are involved in surfactant release and that intact microtubular and microfilament systems may also be necessary.

Animals↗
PubMed1983

The mechanism of inhibition of mitochondrial oxidative phosphorylation by the nonsteroidal anti-inflammatory agent diflunisal.

The anti-inflammatory agent diflunisal was found to induce a progressive loss of respiratory control in tightly coupled rat liver mitochondria, starting at low concentrations (3.3 microM). This loss of control was accompanied by a stimulation of state 4 respiration in the presence of either succinate or glutamate plus malate as the respiratory substrate. The inhibition of state 3 respiration by oligomycin was released by diflunisal. Mitochondrial ATP hydrolysis was stimulated by diflunisal over the same concentration range that affected state 4 respiration: the stimulation was inhibited by oligomycin. It was concluded that diflunisal was acting as an uncoupler of mitochondrial oxidative phosphorylation. An identical action was found in mitochondria isolated from the livers of mice, rabbits and guinea-pigs. Potencies similar to diflunisal were found with flufenamic acid and mefenamic acid, but other anti-inflammatory agents were either less potent or inactive.

Adenosine Triphosphatases↗
PubMed1982

The effects of a number of non-steroidal anti-inflammatory compounds on parturition in the rat.

A method was developed for assessing non-steroidal anti-inflammatory compounds for their potency in blocking parturition, and prolonging gestation, in the rat. This consisted of injecting compounds into groups of 10 to 13 rat dams twice daily from Day 18 through Day 22 of pregnancy, and comparing the treated dams with appropriate controls on Day 23. The rate of blocked parturition appeared to be positively related to dose of non-steroidal anti-inflammatory agent and, therefore, this model and end-point appeared to be useful for assessing different non-steroidal anti-inflammatory compounds for potency. Among the twenty-seven non-steroidal anti-inflammatory agents evaluated by this method were: ibuprofen, phenylbutazone, tolmetin, flufenamic acid, 2(p-biphenyl) acetic acid, mefenamic acid, aspirin, fenoprofen calcium, flumazole, ketoprofen, naproxen, isoxicam, indomethacin, 2(p-biphenyl) propionic acid, 2(2'-fluoro-4-biphenyl) propionic acid, flurbiprofen, sudoxicam and piroxicam. Piroxicam, sudoxicam, flurbiprofen, 2(p-biphenyl) propionic acid and 2(2'-fluoro-4-biphenyl) propionic acid showed the greatest potency. The relationship between structure and activity and between the blocking of parturition and the inhibition of prostaglandin synthesis are discussed.

Animals↗
PubMed1978

The effects of anti-inflammatory drugs on prostaglandin production by rheumatoid synovial tissue.

The effect of anti-inflammatory drugs on prostaglandin production by rheumatoid synovial tissue has been investigated. Synovial explants were maintained in tissue culture for periods up to six days and PGE2 concentrations in culture were determined by radioimmunoassay. The more potent nonsteroidal inhibitors of PGE2 production and their IC50 (micrometer) values were indomethacin 0.005, flufenamic acid 0.2, flurbiprofen 0.6, ibuprofen 2.0 , naproxen 6.0, phenylbutazone 10.0, and aspirin 20.0. Drugs with weak or insignificant effects were hydroxychloroquin, acetaminophen, azathioprine, chloroquin, penicillamine, gold Na thiomalate, and Na salicylate. Glucocorticoids were potent inhibitors; dexamethasone 0.003, prednisolone 0.01, hydrocortisone 0.03; while mineralocorticoids deoxycorticosterone and aldosterone were inactive at 1.0 micrometer. There is a reasonably good correlation between the IC50 concentrations of the nonsteroidal inhibitors and their peak free plasma concentration achieved during therapy in man. Inhibition of prostaglandin synthesis may contribute to the effects of many but not all anti-inflammatory drugs.

Adrenal Cortex Hormones↗
PubMed1982

Augmentation of concanavalin A-induced immunosuppression by indomethacin.

These studies show that, in BALB/C mice, when antibody synthesis against sheep red blood cells is suppressed by concanavalin A, treatment with indomethacin (4-8 mg/kg per os) will augment this suppression. Two other nonsteroidal anti-inflammatory drugs, flufenamic acid and meclofenamic acid (50 mg/kg), also have this effect, whereas phenylbutazone was inactive at this dose. The augmentation of concanavalin A-induced immunosuppression by indomethacin could not be demonstrated on the response to the T-independent antigen polyvinypyrrolidone. In contrast to indomethacin, which inhibits cyclooxygenase, neither nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway, nor eicosa-5,8,11,14-tetraynoic acid, an inhibitor of both the cyclooxygenase and the lipoxygenase pathways, had this augmenting effect. Therefore, we do not have strong evidence that the absence of a prostaglandin is responsible for the effect of indomethacin. However, inhibition of the pathway leading to prostaglandin synthesis causes an increase in arachidonic acid metabolism via the lipoxygenase pathway. A product of this pathway, such as a leukotriene, may have immunosuppressive effects in this model. Evidence for the enhancement of a suppressor cell population is provided by an in vitro coculture assay. Cells treated with concanavalin A and indomethacin had more suppressive activity than cells treated with concanavalin A or indomethacin alone.

Animals↗
PubMed1980

Role of steroid hormones and prostaglandins in the regulation of DNA synthesis by decidual cells in culture.

The effect of oestrogen and progesterone on prostaglandin synthesis and on DNA synthesis by rat decidual cells was studied in a culture system. The cells were explanted from deciduoma either during the proliferation phase (namely on the 5th day of leukocytic smear, Day L5:"L5 cells") or during the maintenance phase ("L8 cells") and examined on the second day of culture. Oestradiol-17 beta (7 X 10(-11) M) and progesterone (6 X 10(-8) M) significantly inhibited accumulation of PGE by cells explanted on Day L5: L8-cell cultures showed no significant response to oestradiol and the progesterone effect was markedly reduced. Progesterone stimulated [3H]thymidine incorporation into cells explanted on Day L5, but had no effect on L8-cultures. Other inhibitors of PG synthesis, namely cortisol, flufenamic acid and indomethacin, also had a stimulatory effect on DNA synthesis by L5 cells. PGE2 (5-10 micrograms/ml) inhibited DNA synthesis in control, indomethacin-treated and progesterone-treated L5-cell cultures, suggesting that the progesterone-induced stimulation of DNA synthesis may be in part be due to its inhibitory effect on PGE accumulation by decidual cells. The possibility is discussed that during the proliferation phase of decidual development in vivo, the rate of DNA synthesis may be influenced by steroid-induced changes in PGE content of the tissue.

Animals↗
PubMed1987

Ovine ureteral motility as a new assay for the cyclo-oxygenase blocking potency of non steroidal anti-inflammatory drugs.

Isolated sheep ureteral ring suspended in an organ bath exhibits rhythmic contractions which are dose-dependently inhibited by indomethacin and revived by prostaglandin E2 or F2 alpha. Seven non-steroidal anti-inflammatory drugs (NSAID) belonging to different chemical groups were tested on the isolated ureteral ring model in molar concentrations of 10(-8)-10(-4) to determine the time elapsing from application of test drug to complete inhibition of ureteral contraction ("stop-time"). The descending order of potency of the NSAID was: flurbiprofen greater than indomethacin greater than flufenamic acid greater than tolmetin greater than aspirin greater than phenylbutazone greater than isoxicam. A parallelism was observed in the plot of log concentration of NSAID and "stop-time" amongst all compounds except aspirin and isoxicam. The sheep isolated ring preparation is a simple reproducible biological model for assessment of anti-inflammatory cyclo-oxygenase inhibitory activity of compounds.

Animals↗
PubMed2005

Nonsteroidal anti-inflammatory drugs and their analogues as inhibitors of aldo-keto reductase AKR1C3: new lead compounds for the development of anticancer agents.

Nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin, flufenamic acid, and related compounds have been recently identified as potent inhibitors of AKR1C3. We report that some other NSAIDs (diclofenac and naproxen) also inhibit AKR1C3, with the IC(50) values in the low micromolar range. In order to obtain more information about the structure-activity relationship and to identify new leads, a series of compounds designed on the basis of NSAIDs were synthesized and screened on AKR1C3. The most active compounds were 2-[(2,2-diphenylacetyl)amino]benzoic acid 4 (IC(50)=11microM) and 3-phenoxybenzoic acid 10 (IC(50)=0.68microM). These compounds represent promising starting points for the development of new anticancer agents.

3-Hydroxysteroid Dehydrogenases↗
PubMed2004

Enzymology of a carbonyl reduction clearance pathway for the HIV integrase inhibitor, S-1360: role of human liver cytosolic aldo-keto reductases.

S-1360, a 1,3-diketone derivative, was the first HIV integrase inhibitor to enter human trials. Clinical data suggested involvement of non-cytochrome P450 clearance pathways, including reduction and glucuronidation. Reduction of S-1360 generates a key metabolite in humans, designated HP1, and constitutes a major clearance pathway. For characterization of subcellular location and cofactor dependence of HP1 formation, [(14)C]-S-1360 was incubated with commercially available pooled human liver fractions, including microsomes, cytosol, and mitochondria, followed by HPLC analysis with radiochemical detection. Incubations were performed in the presence and absence of the cofactors NADH or NADPH. Results showed that the enzyme system responsible for generation of HP1 in vitro is cytosolic and NADPH-dependent, implicating aldo-keto reductases (AKRs) and/or short-chain dehydrogenases/reductases (SDRs). A validated LC/MS/MS method was developed for investigating the reduction of S-1360 in detail. The reduction reaction exhibited sigmoidal kinetics with a K(m,app) of 2 microM and a Hill coefficient of 2. The ratio of V(max)/K(m) was approximately 1 ml/(min mg cytosolic protein). The S-1360 kinetic data were consistent with positive cooperativity and a single enzyme system. The relative contributions of AKRs and SDRs were examined through the use of chemical inhibitors. For these experiments, non-radiolabeled S-1360 was incubated with pooled human liver cytosol and NADPH in the presence of inhibitors, followed by quantitation of HP1 by LC/MS/MS. Quercetin and menadione produced approximately 30% inhibition at a concentration of 100 microM. Enzymes sensitive to these inhibitors include the carbonyl reductases (CRs), a subset of the SDR enzyme family predominantly located in the cytosol. Flufenamic acid and phenolphthalein were the most potent inhibitors, with > 67% inhibition at a concentration of 20 microM, implicating the AKR enzyme family. The cofactor dependence, subcellular location, and chemical inhibitor results implicated the aldo-keto reductase family of enzymes as the most likely pathway for generation of the major metabolite HP1 from S-1360.

Alcohol Oxidoreductases↗
PubMed2006

A TRPC-like non-selective cation current activated by alpha 1-adrenoceptors in rat mesenteric artery smooth muscle cells.

The TRPC family of non-selective cation channels has been suggested to play a key role in the responses to alpha1-adrenoceptor stimulation of vascular smooth muscle. However, there are still very few reports of non-selective cation currents activated by alpha1-AR in resistance arteries. Here, we examine the expression of TRPC channels and the currents activated by alpha1-adrenoceptors in rat mesenteric resistance artery smooth muscle. Messenger RNA and protein for TRPC1, TRPC3 and TRPC6 were detected within the arteries by RT-PCR and immunoblotting. Endothelial and adventitial layers were found to express the TRPC1, TRPC3 and TRPC6 proteins whereas only TRPC1 and TRPC6 were detected in the arterial smooth muscle by confocal immunofluorescence microscopy. In whole-cell patch-clamp recordings from isolated mesenteric arterial myocytes, an outwardly rectifying non-selective cation current was activated by both the alpha1-adrenoceptor agonist, phenylephrine (10 microM), and the diacylglycerol analogue, 1-oleoyl-2-acetyl-sn-glycerol (100 microM). Responses to 1-oleoyl-2-acetyl-sn-glycerol were not blocked, but increased, following inhibition of protein-kinase-C with either bisindolylmaleimide-I (1 microM) or chelerythrine (1 microM). The currents activated by both phenylephrine and 1-oleoyl-2-acetyl-sn-glycerol were inhibited by Gd3+ (100 microM) but potentiated by flufenamic acid (100 microM). Collectively, these findings demonstrate for the first time the expression of TRPC1 and TRPC6 in rat mesenteric artery smooth muscle and the existence in rat isolated mesenteric arterial myocytes of a TRPC-like non-selective cation current activated by alpha1-adrenoceptor stimulation and 1-oleoyl-2-acetyl-sn-glycerol.

Animals↗
PubMed2004

Micellar electrokinetic chromatography for the simultaneous determination of ketorolac tromethamine and its impurities. Multivariate optimization and validation.

A simple, fast and selective micellar electrokinetic chromatographic (MEKC) method for the simultaneous assay of ketorolac tromethamine and its known related impurities (1-hydroxy analog of ketorolac, 1-keto analog of ketorolac and decarboxylated ketorolac), in both drug substance and coated tablets, is described. The compounds were detected at 323 nm, and flufenamic acid (FL) and tolmetin (TL) were chosen as internal standards to quantify ketorolac tromethamine and impurities, respectively. The multivariate optimization of the experimental conditions was carried out by means of the response surface study, considering as responses the resolution values and analysis time. The optimized background electrolyte (BGE) consisted of a mixture of 13 mM boric acid and phosphoric acid, adjusted to pH 9.1 with 1 M sodium hydroxide, containing 73 mM sodium dodecyl sulfate (SDS). Optimal temperature and voltage were 30 degrees C and 27 kV. Applying these conditions, all compounds were resolved in about 6 min. The related substances could be quantified up to the 0.1% (w/w) level. Validation was performed, either for drug substances and drug product, evaluating selectivity, robustness, linearity and range, precision, accuracy, detection and quantitation limits and system suitability.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

Analysis of ketorolac and its related impurities by capillary electrochromatography.

Capillary electrochromatography (CEC) was employed for the assay of ketorolac (KT) and its known related impurities [1-hydroxy analog of ketorolac (HK), 1-keto analog of ketorolac (KK), ketorolac decarboxylated (DK)] in both drug substance and coated tablets. Detection was made at 323 nm and flufenamic acid was selected as internal standard. The experiments were performed in a 100 microm i.d. capillary packed with RP-18 silica particles (33.0, 24.5, 23.0 cm total, effective and packed lengths, respectively). The composition of the mobile phase was optimised by changing pH of the buffer and acetonitrile (ACN) content and by addition of other organic modifiers (methanol, ethanol, isopropanol, n-propanol) in order to evaluate the effect of these factors on the method performance (efficiency, retention and resolution). The optimum mobile phase consisted of a mixture of 50 mM ammonium formate buffer pH 3.5-water-acetonitrile (10:20:70, v/v/v), while voltage and temperature were set at 30 kV and 20 degrees C, respectively. Applying these conditions, all peaks were baseline resolved and the analysis was performed in less than 9 min. Selectivity, repeatability of retention time and peak area, detection and quantitation limits, linearity and range, precision and accuracy were also investigated. R.S.D. and bias values obtained for all the analytes were below 5% and sensitivity was satisfactory, thus the method was deemed suitable for pharmaceutical quality control. Applying the method to coated tablets, a recovery of 98.5+/-0.8% and an R.S.D. of 0.5% were found.

Calibration↗
PubMed2004

Substance P induces inward current and regulates pacemaker currents through tachykinin NK1 receptor in cultured interstitial cells of Cajal of murine small intestine.

We investigated whether substance P modulates pacemaker currents generated in cultured interstitial cells of Cajal of murine small intestine using whole cell patch-clamp techniques at 30 degrees C. Interstitial cells of Cajal generated spontaneous inward currents (pacemaker currents) at a holding potential of -70 mV. Tetrodotoxin, nifedipine, tetraethylammonium, 4-aminopyridine, or glibenclamide did not change the frequency and amplitude of pacemaker currents. However, divalent cations (Ni2+, Mn2+, Cd2+, and Co2+), nonselective cationic channel blockers (gadolinium and flufenamic acid), and a reduction of external Na+ from normal to 1 mM inhibited pacemaker currents indicating that nonselective cation channels are involved in their generation. Substance P depolarized the membrane potential in current clamp mode and produced tonic inward pacemaker currents with reduced frequency and amplitude in voltage clamp mode. [D-Arg1, D-Trp7,9, Leu11] substance P, a tachykinin NK1 receptor antagonist, blocked these substance P-induced responses. Furthermore, [Sar9, Met(O2)11] substance P, a specific tachykinin NK1 receptor agonist, depolarized the membrane and tonic inward currents mimicked those of substance P. Substance P continued to produce tonic inward currents in external Ca2+-free solution or in the presence of chelerythrine, a protein kinase C inhibitor. However, substance P-induced tonic inward currents were blocked by thapsigargin, a Ca2+-ATPase inhibitor in the endoplasmic reticulum or by an external 1 mM Na+ solution. Our results demonstrate that substance P may modulate intestinal motility by acting on the interstitial cells of Cajal by activating nonselective cation channels via the release of intracellular Ca2+ induced by tachykinin NK1 receptor stimulation.

4-Aminopyridine↗
PubMed2005

Actions of glutamate and ivermectin on the pharyngeal muscle of Ascaridia galli: a comparative study with Caenorhabditis elegans.

The actions of glutamate and ivermectin were examined in the pharynx of Ascaridia galli and the results compared with those on the pharynx of Caenorhabditis elegans. In both preparations glutamate elicits a depolarization and inhibition of pharyngeal pumping, but the response of the pharynx of A. galli was much less than for C. elegans. This may be either because the pharyngeal membrane potential of the former is closely linked to the equilibrium potential for chloride ions (E(Cl)) while that of C. elegans is independent of E(Cl), or that there is a lower density of glutamate receptors on the pharyngeal muscle of A. galli compared with C. elegans. The maximum depolarization to glutamate of the pharyngeal muscle was 4.5+/-0.8 mV in A. galli while it was >25 mV in C. elegans. Picrotoxin was a weak antagonist of the glutamate response in both species. Flufenamic acid, pentobarbitone and flurazepam had no significant effect on either preparation at concentrations up to 100 microM. Three glutamate receptor agonists, ibotenate, kainate and quisqualate were all more potent than glutamate on the A. galli pharyngeal muscle. In contrast, only ibotenate was more potent than glutamate in C. elegans pharynx, the other two agonists being approximately 20 times less potent. The potency of ivermectin differed markedly between the two species, being approximately three orders of magnitude less potent on the pharynx of A. galli compared with C. elegans. This study demonstrates clear differences between the properties of the pharyngeal muscle of the two species and shows that care must be taken when extrapolating data from free-living to parasitic species of nematode.

Action Potentials↗
PubMed2005

Mechanisms of Na+ and Ca2+ influx into respiratory neurons during hypoxia.

Changes in intracellular Na+ and Ca2+ in inspiratory neurons of neonatal mice were examined by using ion-selective fluorescent indicator dyes SBFI and fura-2, respectively. Both [Na+]i and [Ca2+]i signals showed rhythmic elevations, correlating with the inspiratory motor output. Brief (2-3 min) hypoxia, induced initial potentiation of rhythmic transients followed by their depression. During hypoxia, the basal [Na+]i and [Ca2+]i levels slowly increased, reflecting development of an inward current (Im). By antagonizing specific mechanisms of Na+ and Ca2+ transport we found that increases in [Na+]i, [Ca2+]i and Im due to hypoxia are suppressed by CNQX, nifedipine, riluzole and flufenamic acid, indicating contribution of AMPA/kainate receptors, persistent Na+ channels, L-type Ca2+ channels and Ca2+-sensitive non-selective cationic channels, respectively. The blockers decreased also the amplitude of the inspiratory bursts. Modification of mitochondrial properties with FCCP and cyclosporine A decreased [Ca2+]i elevations due to hypoxia by about 25%. After depletion of internal Ca2+ stores with thapsigargin, the blockade of NMDA receptors, Na+/K+ pump, Na+/H+ and Na+/Ca2+ exchange, the hypoxic response was not changed. We conclude that slow [Na+]i and [Ca2+]i increases in inspiratory neurons during hypoxia are caused by Na+ and Ca2+ entry due to combined activation of persistent Na+ and L-type Ca2+ channels and AMPA/kainate receptors.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2004

Amyloidosis: a clinico-pathophysiological synopsis.

Amyloidosis encompasses a spectrum of diseases in which there is disordered folding of certain proteins that leads to them being deposited as insoluble fibrils in the extracellular space. The result of this process is impaired tissue structure and function. Amyloidosis may be acquired or hereditary and local or systemic, and is defined according to the identity of the fibril precursor protein. Over 20 unrelated proteins can form amyloid fibrils in vivo, which all share a lamellar cross-beta-sheet structure composed of non-covalently associated protein or peptide subunits. Glycosaminoglycans and the pentraxin protein, serum amyloid P component, are universal non-fibrillar constituents of amyloid deposits that are believed to play a role in fibrillogenesis and fibril persistence. Greater understanding of the processes underlying amyloidogenesis, at all levels from cellular to clinical, has led to improvements in diagnosis, monitoring and treatment of this group of diseases, as well as pointing to possible future therapies.

Acetylglucosamine↗
PubMed1998

Hyperpolarization of the cell membrane of mouse hepatocytes by lactate, pyruvate, and fructose is due to Ca2+-dependent activation of K+ channels and of the Na+/K+-ATPase.

Using superfused mouse liver slices combined with a conventional microelectrode technique, we investigated: (1) the ionic mechanisms involved in the hyperpolarization of the hepatocyte membrane induced by lactate and other gluconeogenic substrates; (2) whether these mechanisms are similar to those underlying the hyperpolarization induced by cell swelling in hypo-osmotic medium; and (3) whether the hyperpolarizing effect of lactate on the hepatocyte membrane is related to gluconeogenesis. Lactate (5 mmol/l) hyperpolarized the hepatocyte membrane after an exposure of 10-20 min, and the hyperpolarization was still present after 70 min. The hyperpolarization induced by lactate, pyruvate (5 mmol/l) and fructose (10 mmol/l), and by exposure to hypo-osmotic medium (250 mosmol/l) was antagonized by ouabain, tetraethylammonium (TEA), and cetiedil (lactate; hypo-osmotic medium). Hyperpolarization induced by lactate was eliminated or attenuated by agents impairing activation of Ca2+-dependent K+ channels, by amiloride, and by a blockade of non-selective cation channels with flufenamic acid and gadolinium. Thapsigargin, increasing cytosolic Ca2+, mimicked lactate's hyperpolarizing effect. Lactate's effect was dependent on extracellular Ca2+. Finally, lactate's hyperpolarizing effect was reduced by inhibiting gluconeogenesis. These findings suggest that metabolism of lactate hyperpolarizes hepatocytes by mechanisms analogous to those underlying the hyperpolarization induced by cell swelling in hypo-osmotic medium. Gluconeogenesis from lactate may cause cell swelling, subsequent activation of Ca2+-dependent K+ channels and of the Na+/K+-ATPase, and thus hyperpolarize the hepatocyte membrane.

Amiloride↗