benzofurans and Hypoxia

To assess the potential effect of dl-3-N-butylphthalide (dl-NBP) for the proliferation and differentiation of neural stem cells (NSCs) against hypoxia and the underlying mechanism.. Hippocampal NSCs were obtained from fetal rats. NSCs combined with dl-NBP and single NSCs were cultured. The impact of siRNA-mediated hypoxia-inducible factor-1alpha (HIF-1α) knockdown on NSCs was detected with western blotting (WB) and quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR). Cell-counting kit-8 assay was used for evaluating the viability of NSCs. Levels of HIF-1α protein were measured using WB, and vascular endothelial growth factor (VEGF) expression was quantified using RT-qPCR and enzyme-linked immunosorbent assay.. Compared with 7 different concentrations of dl-NBP, 0.25 g/L was determined as the optimal concentration to significantly increase the viability of NSCs (p < 0.001). Dl-NBP can significantly increase the viability of hypoxic NSCs (p < 0.001) and improve the differentiation of hypoxic NSCs into astrocytes (p = 0.001) and oligodendrocytes (p < 0.001). Meanwhile, Dl-NBP can significantly elevate levels of HIF-1α protein (p < 0.001) and VEGF mRNA (p = 0.001) / protein (p < 0.001) in NSCs in the hypoxic environment. However, after transfection with HIF-1α siRNA in NSCs, the viability and differentiation of NSCs was not recovered using dl-NBP under the hypoxic condition, as well as levels of HIF-1α and VEGF.. Dl-NBP can reverse the weaker proliferation and differentiation power of NSCs in the hypoxic environment. The HIF-1α - VEGF pathway may be implicated in this protective effect of dl-NBP.

Topics: Animals; Benzofurans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Neural Stem Cells; Neuroprotective Agents; Rats

Psoralidin (PSO) is a natural phenolic coumarin extracted from the seeds of Psoralea corylifolia L. Growing preclinical evidence indicates that PSO has anti-inflammatory, anti-vitiligo, anti-bacterial, and anti-viral effects. Growth arrest-specific gene 6 (GAS6) and its receptor, Axl, modulate cellular oxidative stress, apoptosis, survival, proliferation, migration, and mitogenesis. Notably, the neuroprotective role of the GAS6/Axl axis has been identified in previous studies. We hypothesize that PSO ameliorates cerebral hypoxia/reoxygenation (HR) injury via activating the GAS6/Axl signaling. We first confirmed that PSO was not toxic to the cells and upregulated GAS6 and Axl expression after HR injury. Moreover, PSO exerted a marked neuroprotective effect against HR injury, represented by restored cell viability and cell morphology, decreased lactate dehydrogenase (LDH) release, and reactive oxygen species (ROS) generation. Furthermore, PSO pretreatment also elevated the levels of nuclear factor-related factor 2 (Nrf-2), NAD(P)H dehydrogenase quinone-1 (NQO1), heme oxygenase-1 (HO-1), silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF1), uncoupling protein 2 (UCP2), and B-cell lymphoma 2 (BCl2) both in the condition of baseline and HR injury. However, GAS6 siRNA or Axl siRNA inhibited the neuroprotective effects of PSO. Our findings suggest that PSO pretreatment attenuated HR-induced oxidative stress, apoptosis, and mitochondrial dysfunction in neuroblastoma cells through the activation of GAS6/Axl signaling.

Topics: Benzofurans; Coumarins; Humans; Hypoxia; Hypoxia, Brain; Intercellular Signaling Peptides and Proteins; Neuroprotective Agents; Proto-Oncogene Proteins; Receptor Protein-Tyrosine Kinases; RNA, Small Interfering

Salvianolic acid B (SalB) has been extensively investigated in our laboratory for myocardial ischemia (MI) disease. This study mainly aimed to illustrate the relationship between SIRT1 and the therapeutic effect of SalB on MI in rats and hypoxia damage in H9c2 cells. Furthermore, whether the antagonism of NLRP3 by SalB in the injuries mentioned above is related to SIRT1-AMPK-PGC-1α pathway-mediated mitochondrial biogenesis was further investigated. In vivo, 24 h after MI surgery, we found that SalB effectively reduced ST-segment elevation, myocardial infarct size enlargement, cardiac injury markers, myocardial structural abnormalities, and myocardial apoptotic cells in MI injury rats. In vitro, after 4 h of hypoxia exposure, SalB alleviated cell injury, inhibited the production of ROS and IL-1β, and prevented the loss of mitochondrial membrane potential (MMP). Besides, SalB downregulated the critical components of the NLRP3 inflammasome and upregulated the SIRT1-AMPK-PGC-1α signaling pathway-related molecules in myocardial tissues and H9c2 cells. However, all the above protective effects of SalB on MI could be offset by EX527. Taken together, our findings indicated that SalB could attenuate MI injury by targeting NLRP3, which is at least partially dependent on the SIRT1/AMPK/PGC-1α signaling pathway.

Topics: AMP-Activated Protein Kinases; Animals; Benzofurans; Cardiomegaly; Hypoxia; Inflammasomes; Myocardial Ischemia; NLR Family, Pyrin Domain-Containing 3 Protein; Rats; Rats, Sprague-Dawley; Signal Transduction; Sirtuin 1

Topics: Animals; Apoptosis; Benzofurans; Brain Ischemia; Cell Line; Cell Line, Tumor; Drug Design; Edaravone; Glucose; Humans; Hydrogen Peroxide; Hypoxia; Infarction, Middle Cerebral Artery; Male; Neuroprotective Agents; NF-E2-Related Factor 2; Oxidative Stress; Oxygen; Platelet Aggregation; Rats; Rats, Sprague-Dawley; Reperfusion Injury

The aim of this paper was to investigate whether the mechanism of salvianolic acid B in protecting H9 c2 cardiomyocytes from hypoxia/reoxygenation injury is related to the regulation of mitochondrial autophagy mediated by NIX. H9 c2 cardiomyocytes were cultured in vitro and divided into normal group, model group and salvianolic acid B group(50 μmol·L~(-1)). Hypoxia/reoxygenation injury model was established by hypoxia for 4 h and reoxygenation for 2 h. In normal group, high glucose DMEM medium was used for culture. Those in model group were cultured with DMEM medium without glucose and oxygen, and no drugs for hypoxia and reoxyge-nation. In salvianolic acid B group, salvianolic acid B prepared by glucose-free DMEM medium was added during hypoxia, and the other process was as same as the model group. The cell viability was evaluated by CCK-8 assay. The leakage of lactate dehydrogenase(LDH) was detected by microplate method. The levels of intracellular reactive oxygen species(ROS) and mitochondrial membrane potential(ΔΨm) were measured by chemical fluorescence method. The level of intracellular adenosine triphosphate(ATP) was mea-sured by fluorescein enzyme method. The autophagy related proteins LC3-Ⅰ, LC3-Ⅱ, apoptosis related protein cleaved caspase-3 and mitochondrial autophagy receptor protein NIX were detected by Western blot. As compared with the normal group, the activity of H9 c2 cardiomyocytes and ATP level were decreased(P<0.05); LDH leakage and ROS production were increased(P<0.01); ΔΨm was decreased(P<0.01); LC3-Ⅱ/LC3-Ⅰ ratio, cleaved caspase-3 and NIX protein expression levels were increased(all P<0.05) in the model group. As compared with the model group, the activity of cells and ΔΨm were significantly increased(P<0.01); ATP level was increased(P<0.05); LDH leakage and ROS generation were decreased(P<0.01); LC3-Ⅱ/LC3-Ⅰ ratio was decreased(P<0.01); cleaved caspase-3 and NIX expression levels were decreased(P<0.05) in the salvianolic acid B group. The protective effect of salvianolic acid B on hypoxia/reoxygenation injury of H9 c2 cardiomyocytes may be associated with inhibiting mitochondrial auto-phagy. The specific mechanism may be related to inhibiting the activation of mitochondrial autophagy mediated by NIX, increasing ΔΨm, reducing ROS production, reducing the expression of cleaved caspase-3, LC3-Ⅱ, and increasing cell viability.

Topics: Apoptosis; Autophagy; Benzofurans; Cell Hypoxia; Cell Survival; Humans; Hypoxia; Myocytes, Cardiac

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common type of pancreatic cancer, and has still been the medicinal mystery. New drugs and treatment strategies are urgently needed. In this study, 32 benzofuran derivatives are designed, synthesized and evaluated as potential agents against the pancreatic cancer. Among them, compound 9o with the best physicochemical and pharmacokinetic properties exhibited excellent cytotoxicity against many tumor cell lines. In vivo study showed that compound 9o dramatically suppressed the tumor growth of nude mice. Furthermore, compound 9o could affect the hypoxia environment through Hif-1α/VEGF pathway, resulting in the anti-angiogenic activity. These studies indicated that compound 9o was a promising candidate for the treatment of PDAC, deserving further studies.

Topics: Animals; Antineoplastic Agents; Benzofurans; Cell Proliferation; Dose-Response Relationship, Drug; Drug Design; Drug Screening Assays, Antitumor; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Mice; Molecular Structure; Neoplasms, Experimental; Pancreatic Neoplasms; Structure-Activity Relationship; Tumor Cells, Cultured

Hypoxia-induced epithelial-mesenchymal transition (EMT) has been identified as essential for tumor progression and metastasis. The present study examined the effects of an antioxidant, dieckol, on hypoxia‑induced EMT in HT29 human colorectal cancer cells. HT29 cells were treated with a hypoxia‑inducing agent, CoCl2, and an increase in the levels of intracellular reactive oxygen species (ROS) and various morphological changes, such as loss of cell‑cell contact and aggressive cell migration were observed. CoCl2 also induced an increase in the expression of hypoxia‑inducible factor 1α (HIF1α) and various mesenchymal‑specific markers, including vimentin and snail family transcriptional repressor 1 (Snail1), and a decrease in the expression of E‑cadherin, thus suggesting that CoCl2 induced EMT in HT29 cells. Conversely, the CoCl2‑induced EMT of HT29 cells was suppressed following treatment with dieckol. In addition, ROS generation, EMT marker protein expression and intracellular localization, cell migration and cell invasion were attenuated following dieckol treatment. The findings of the present study suggested that dieckol may inhibit hypoxia‑induced EMT in HT29 cells by regulating the levels of cellular ROS and protein expression levels downstream of the HIF1α signaling pathway. Therefore, dieckol has the potential to become an attractive therapeutic agent for the treatment of colorectal cancer.

Topics: Benzofurans; Cell Line, Tumor; Cell Movement; Cell Survival; Colorectal Neoplasms; Epithelial-Mesenchymal Transition; HT29 Cells; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Phenotype; Reactive Oxygen Species; Signal Transduction

Enhancer regulation is a new control mechanism in the brain [Knoll, J., 2003. Enhancer regulation/endogenous and synthetic enhancer compounds: a neurochemical concept of the innate and acquired drives. Neurochemical Research 28(8), 1275-1297]. Enhancer substances exert their effect in bi-modal form with a highly characteristic dose-dependency. Two bell-shaped concentration curves have been published. The one in ultra low concentration range (fM) specific form of enhancer regulation and the other at high concentration (100 microM) non-specific form of enhancer regulation. Catecholaminergic neurons proved to be enhancer-sensitive cells. Since rat PC12 cells and human brain endothelial cells (HBEC) work under catecholaminergic influence, it was reasonable to expect that both the specific and non-specific form of the enhancer regulation might be detectable in these cells. We tested this possibility on these cultured cells under normoxia and hypoxia-reoxygenation. After 1 h hypoxia produced by Argon gas and 0, 2, 4, and 20 h reoxygenation the cell loss was calculated by propidiumiodide assay and the cell activity was investigated by Alamar Blue assay colorimetric measurement. The percentages of living and necrotic cells were expressed after propidiumiodide staining. Broad scale concentrations of the two compounds (1 fM-100 microM) were added to the culture strait after the oxygen deprivation. (-)-BPAP and (-)-deprenyl, due to their enhancer effect, exerted a significant cytoprotective effect on both HBECs and PC12 cells. In harmony with Knoll's publications we were able to demonstrate by the aid of (-)-BPAP and (-)-deprenyl that both HBEC and PC12 are enhancer-sensitive cells. We detected the specific form of the enhancer regulation in the ultra low concentration range (fM-pM) and also the non-specific form of the enhancer regulation was visible (mM-microM).

Topics: Animals; Benzofurans; Brain; Capillaries; Cells, Cultured; Cytoprotection; Endothelial Cells; Humans; Hypoxia; Neuroprotective Agents; Oxidation-Reduction; PC12 Cells; Rats; Selegiline

The potential of fly ash to dechlorinate and destroy PCDD, PCDF and PCB was tested under oxygen deficient conditions in the laboratory. Specifically, two types of fly ash were compared, originating either from a fluidized bed incinerator using Ca(OH)2 spray (FA1), or a stoker incinerator without Ca(OH)2 impact (FA2). Results from the present study indicate that on FA2 type fly ash, the degradation processes of OCDD, OCDF and D10CB occurred primarily via dechlorination/hydrogenation up to temperature settings of 340 degrees C. In contrast, FAI type fly ash was found to effect both dechlorination and destruction of these compounds already at temperature settings of 260 degrees C. The dechlorination velocity of PCDD and PCDF did not differ significantly. However, the first dechlorination step of OCDF in the 1,9-position occurred faster compared to the first dechlorination step of OCDD. The isomer pattern resulting from the dechlorination processes was quite similar on both FAI and FA2, indicating that differences in alkalinity or elemental composition of the two types of fly ashes do not have a significant influence on the position of dechlorination. PCDD and PCDF dechlorination of the 2,3,7,8-positions was not favoured over dechlorination of the 1,4.6,9-positions on either type of fly ash. In contrast, dechlorination of PCB occurred predominantly on the toxicological relevant 3- and 4-positions. The dechlorination/destruction processes were completed on both types of fly ash at 380 degrees C within one hour, which correlates well with results obtained from actual plant operation practices.

Topics: Air Pollution; Benzofurans; Dibenzofurans, Polychlorinated; Environmental Monitoring; Environmental Pollutants; Hypoxia; Incineration; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Refuse Disposal; Soil Pollutants; Temperature

The effects of SB 217242, a non-peptide endothelin (ET) receptor antagonist, were investigated against hypoxia-induced cardiopulmonary changes in high altitude-sensitive rats. In isolated pulmonary artery rings, SB 217242 (30 n m) antagonized ET-1-induced contractions with a p KB of 8.0. There was no difference in the sensitivity to ET-1 or the potency of SB 217242 in pulmonary artery from normoxic rats vs. rats exposed to hypoxia (9% O2) for 14 days. However, there was a marked reduction in the maximum response to ET-1, but not to KCl or phenylephrine, in pulmonary artery from hypoxic rats; this phenomenon was inhibited by treatment of animals with SB 217242 (10.8 mg/day, ip by osmotic pump) for the 14-day hypoxic period. Furthermore, there was a significant reduction in carbachol-induced, endothelium-dependent relaxation of precontracted pulmonary artery from hypoxic animals; SB 217242 treatment during the hypoxic period did not influence this difference. Vehicle-treated rats exposed to 14-day hypoxia had 173% higher pulmonary artery pressures and 75% higher right/left+septum ventricular mass ratios compared to normoxic animals. SB 217242 (3.6 or 10.8 mg/day, ip) markedly reduced (80 and 95%, respectively) hypoxia-induced increases in pulmonary artery pressure. Right ventricular hypertrophy was inhibited by 40% at the 10.8 mg/day dose. Marked medial thickening and luminal stenosis of small and medium-sized pulmonary arteries was observed in hypoxic rats. The SB 217242-treated, hypoxia-exposed rats had comparable small and medium-sized arteries to normoxic rats. Rats treated with SB 217242 (10.8 mg/day) for the last 14 days of a 28-day hypoxic exposure had significantly lower pulmonary artery pressures than those of vehicle-treated rats. In addition, the effects of the selective ETA receptor antagonist, SB 247083, and the selective ETB receptor antagonist, A-192621 (3.6 or 10.8 mg/day, ip), were compared against hypoxia-induced increases in pulmonary artery pressure and plasma ET concentrations. SB 247083, but not A-192621, inhibited hypoxia-induced pulmonary hypertension, whereas A-192621, but not SB 247083, significantly exacerbated hypoxia-induced increases in ET concentrations, suggesting that hypoxia-induced pulmonary pressor responses are mediated via ETA receptor activation, while ETB receptor blockade may alter clearance of hypoxia-induced elevated plasma ET. The inhibitory effects of SB 217242 on the functional and remodeling changes induced by

Topics: Altitude; Animals; Benzofurans; Carboxylic Acids; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Indans; Male; Propionates; Pulmonary Artery; Pyrrolidines; Random Allocation; Rats; Receptors, Endothelin

The role of the Na+/H+ exchanger in rat hearts during ischemia and reperfusion was investigated by measurements of intracellular Na+ concentration ([Na+]i) and intracellular and extracellular pH. Under our standard conditions (2-Hz stimulation), 10 min of ischemia caused no significant rise in [Na+]i but an acidosis of 1.0 pH unit, suggesting that the Na+/H+ exchanger was inactive during ischemia. This was confirmed by showing that the Na+/H+ exchange inhibitor methylisobutyl amiloride (MIA) had no effect on [Na+]i or on intracellular pH during ischemia. However, there was a short-lived increase in [Na+]i of 8.2 +/- 0.6 mM on reperfusion, which was reduced by MIA, showing that the Na+/H+ exchanger became active on reperfusion. To investigate the role of metabolic changes, we measured [Na+]i during anoxia. The [Na+]i did not change during 10 min of anoxia, but there was a small, transient rise of [Na+]i on reoxygenation, which was inhibited by MIA. In addition, we show that the Na+/H+ exchanger, tested by sodium lactate exposure, was inhibited during anoxia. These results show that the Na+/H+ exchanger is inhibited during ischemia and anoxia, probably by an intracellular metabolic mechanism. The exchanger activates rapidly on reperfusion and can cause a rapid rise in [Na+]i.

Topics: Acidosis; Amiloride; Animals; Benzofurans; Benzopyrans; Ethers, Cyclic; Female; Fluorescent Dyes; Heart Ventricles; Hydrogen-Ion Concentration; Hypoxia; Muscle Fibers, Skeletal; Myocardial Ischemia; Myocardium; Naphthols; Organ Culture Techniques; Rats; Rats, Sprague-Dawley; Rhodamines; Sodium; Sodium Lactate; Sodium-Hydrogen Exchangers; Ventricular Function, Left

1. Angiotensin II (AII) binding density and the effect of chronic AII receptor blockade were examined in the rat model of hypoxia-induced pulmonary hypertension. 2. [125I]-[Sar1,Ile2]AII binding capacity was increased in lung membranes from rats exposed to hypoxia (10% fractional inspired O2) for 7 days compared to normal rats (Bmax 108 +/- 12 vs 77 +/- 3 fmol mg-1 protein; P < 0.05), with no significant change in dissociation constant. Competition with specific AII receptor subtype antagonists demonstrated that AT1 is the predominant subtype in both normal and hypoxic lung. 3. Rats treated intravenously with the AT1 antagonist, GR138950C, 1 mg kg-1 day-1 rather than saline alone during 7 days of exposure to hypoxia developed less pulmonary hypertension (pulmonary arterial pressure: 21.3 +/- 1.7 vs 28.3 +/- 1.1 mmHg; P < 0.05), right ventricular hypertrophy (right/left ventricle weight ratio: 0.35 +/- 0.01 vs 0.45 +/- 0.01; P < 0.05) and pulmonary artery remodelling (abundance of thick-walled pulmonary vessels: 9.6 +/- 1.4% vs 20.1 +/- 0.9%; P < 0.05). 4. The reduction in cardiac hypertrophy and pulmonary remodelling with the AT1 antagonist was greater than that achieved by a dose of sodium nitroprusside (SNP) that produced a comparable attenuation of the rise in pulmonary arterial pressure during hypoxia. 5. The data suggest that AII, via the AT1 receptor, has a role in the early pathogenesis of hypoxia-induced pulmonary hypertension in the rat.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Angiotensin II; Angiotensin Receptor Antagonists; Animals; Benzofurans; Hypertension, Pulmonary; Hypoxia; Lung; Male; Nitroprusside; Prostaglandin Endoperoxides, Synthetic; Rats; Rats, Wistar; Receptors, Angiotensin; Thromboxane A2

Substantiating evidence has raised the possibility that sigma ligands may have therapeutic potential as neuroprotective agents in brain ischemia. It has been suggested that the neuroprotective capacity of sigma ligands is related primarily to their affinity for the NMDA receptor complex and not to any selective action at the sigma binding site. However, sigma specific ligands, devoid of significant affinity for the NMDA receptor, are also neuroprotective via an inhibition of the ischemic-induced presynaptic release of excitotoxic amino acids. In the present study, we have investigated the potential neuroprotective effect of a comprehensive series of sigma ligands, with either significant (sigma/PCP) or negligible (sigma) affinity for the PCP site of the NMDA receptor, in order to delineate a selective sigma site-dependent neuroprotective effect. For this aim, we have employed two different neuronal culture toxicity paradigms implicating either postsynaptic-mediated neurotoxicity, (brief exposure of cultures to a low concentration of NMDA or Kainate) or pre- and postsynaptic mechanisms (exposure to hypoxic/hypoglycemic conditions). Only sigma ligands with affinity for the NMDA receptor [(+) and (-) cyclazocine, (+) pentazocine, (+) SKF-10047, ifenprodil and haloperidol] were capable of attenuating NMDA-induced toxicity whereas the sigma [(+)BMY-14802, DTG, JO1784, JO1783, and (+)3-PPP] and kappa-opioid [CI-977, U-50488H] ligands, with very low affinity for the NMDA receptor, were inactive. The rank order of potency, based on the 50% protective concentration (PC50) value, of sigma/PCP ligands against NMDA-mediated neurotoxicity correlates with their affinity for the PCP site of the NMDA receptor, and not with their affinity for the sigma site. In addition sigma/PCP, sigma or kappa-opioid ligands failed to attenuate kainate-mediated neurotoxicity. On the other hand, sigma/PCP, sigma and kappa-opioid ligands were potent inhibitors of hypoxia/hypoglycemia-induced neurotoxicity, although their neuroprotective potency did not correlate with their affinity for either the sigma or PCP binding sites. In conclusion, the ability of sigma and kappa-opioid ligands to attenuate hypoxia/hypoglycemia, but not NMDA or kainate-induced toxicity, suggests that these drugs exert their neuroprotective role by a predominantly presynaptic mechanism possibly by inhibiting ischemic-mediated glutamate release.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anti-Arrhythmia Agents; Antihypertensive Agents; Benzofurans; Brain Ischemia; Cell Death; Cells, Cultured; Dizocilpine Maleate; Hypoxia; Kainic Acid; Ligands; N-Methylaspartate; Neurons; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Receptors, Phencyclidine; Receptors, sigma

Studies have shown that the rise in intracellular ionized calcium, [Ca2+]i, in hypoxic myocardium is driven by an increase in sodium, [Na+]i, but the source of Na+ is not known.. Inhibitors of the voltage-gated Na+ channel were used to investigate the effect of Na+ channel blockade on hypoxic Na+ loading, Na(+)-dependent Ca2+ loading, and reoxygenation hypercontracture in isolated adult rat cardiac myocytes. Single electrically stimulated (0.2 Hz) cells were loaded with either SBFI (to index [Na+]i) or indo-1 (to index [Ca2+]i) and exposed to glucose-free hypoxia (PO2 < 0.02 mm Hg). Both [Na+]i and [Ca2+]i increased during hypoxia when cells became inexcitable following ATP-depletion contracture. The hypoxic rise in [Na+]i and [Ca2+]i was significantly attenuated by 1 mumol/L R 56865. Tetrodotoxin (60 mumol/L), a selective Na(+)-channel blocker, also markedly reduced the rise in [Ca2+]i during hypoxia and reoxygenation. Reoxygenation-induced cellular hypercontracture was reduced from 83% (45 of 54 cells) under control conditions to 12% (4 of 32) in the presence of R 56865 (P < .05). Lidocaine reduced hypercontracture dose dependently with 13% of cells hypercontracting in 100 mumol/L lidocaine, 42% in 50 mumol/L lidocaine, and 93% in 25 mumol/L lidocaine. The Na(+)-H+ exchange blocker, ethylisopropylamiloride (10 mumol/L) was also effective, limiting hypercontracture to 12%. R 56865, lidocaine, and ethylisopropylamiloride were also effective in preventing hypercontracture in normoxic myocytes induced by 75 mumol/L veratridine, an agent that impairs Na+ channel inactivation. Ethylisopropylamiloride prevented the veratridine-induced rise in [Ca2+]i without affecting Na(+)-Ca2+ exchange, suggesting that amiloride derivatives can reduce Ca2+ loading by blocking Na+ entry through Na+ channels, an action that may in part underlie their ability to prevent hypoxic Na+ and Ca2+ loading.. Na+ influx through the voltage-gated Na+ channel is an important route of hypoxic Na+ loading, Na(+)-dependent Ca2+ loading, and reoxygenation hypercontracture in isolated rat cardiac myocytes. Importantly, the Na+ channel appears to serve as a route for hypoxic Na+ influx after myocytes become inexcitable.

Topics: Amiloride; Animals; Benzofurans; Benzothiazoles; Calcium; Calcium Channel Blockers; Cell Separation; Ethers, Cyclic; Fluorescent Dyes; Hypoxia; Lidocaine; Myocardial Contraction; Myocardium; Piperidines; Rats; Sodium; Sodium Channel Blockers; Sodium-Hydrogen Exchangers; Tetrodotoxin; Thiazoles

Topics: Benzofurans; Cardiomyopathies; Disease; Electrocardiography; Furans; Heart Diseases; Hypoxia; Myocardium; Vasodilator Agents