A chloride channel in rat pancreatic acinar AR42J cells is sensitive to extracellular acidification and dependent on ROS.

Extracellular acidification, playing a promoting role in the process of acute pancreatitis, has been reported to activate Cl- channels in several types of cells. However, whether extracellular acidification aggravates acute pancreatitis via activating Cl- channels remains unclear. Here, we investigated the effects of extracellular acidification on Cl- channels in rat pancreatic acinar AR42J cells using whole-cell patch-clamp recordings. We found that extracellular acidification induced a moderately outward-rectified Cl- current, with a selectivity sequence of I- > Br- ≥ Cl- > gluconate-, while intracellular acidification failed to induce the currents. The acid-sensitive currents were inhibited by Cl- channel blockers, 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate and 5-Nitro-2-(3-phenylpropylamino) benzoic acid. After ClC-3 was silenced by ClC-3 shRNA, the acid-sensitive Cl- currents were attenuated significantly, indicating that ClC-3 plays a vital role in the induction of acid-sensitive Cl- currents. Extracellular acid elevated the intracellular level of reactive oxygen species (ROS) significantly, prior to inducing Cl- currents. When ROS production was scavenged, the acid-sensitive Cl- currents were abolished. Whereas, the level of acid-induced ROS was unaffected with silence of ClC-3. Our findings above demonstrate that extracellular acidification induces a Cl- current in pancreatic acinar cells via promoting ROS generation, implying an underlying mechanism that extracellular acidification might aggravate acute pancreatitis through Cl- channels.

Starvation-induced autophagy is up-regulated via ROS-mediated ClC-3 chloride channel activation in the nasopharyngeal carcinoma cell line CNE-2Z.

Nutrient deficiency develops frequently in nasopharyngeal carcinoma cell (CNE-2Z) due to the characteristics of aggregation and uncontrolled proliferation. Therefore, starvation can induce autophagy in these cells. Chloride channel 3 (ClC-3), a member of the chloride channel family, is involved in various biological processes. However, whether ClC-3 plays an important role in starvation-induced autophagy is unclear. In this study, Earle's balanced salt solution (EBSS) was used to induce autophagy in CNE-2Z cells. We found that autophagy and the chloride current induced by EBSS were inhibited by chloride channel blockers. ClC-3 knockdown inhibited the degradation of LC3-II and P62. Furthermore, when reactive oxygen species (ROS) generation was suppressed by antioxidant N-acetyl-l-cysteine (L-NAC) pretreatment, EBSS-induced autophagy was inhibited, and the chloride current was unable to be activated. Nevertheless, ClC-3 knockdown had little effect on ROS levels, indicating that ROS acted upstream of ClC-3 and that both ROS and ClC-3 participated in EBSS-induced autophagy regulation in CNE-2Z.

Effect of Lidocaine on Olfactory Perception in Humans.

OBJECTIVE: The effect of local anesthesia to the nasal mucosa on olfactory acuity is the subject of some debate. This study was aimed to investigate the effect of local anesthesia on olfactory perception. MATERIALS AND METHODS: Six healthy participants, five males and one female, were chosen from the academic population of Cardiff University. Olfactory perception was monitored at intervals following administration of 4% lidocaine to the nasal mucosa in the volunteers. Lidocaine was administered using a nasal spray as used in routine otolaryngological investigations. The olfactory stimulus (amyl acetate) was delivered directly to the nostril using an olfactometer. Olfactory perception was determined by the use of a 13 trial, forced choice scoring task. RESULTS: Lidocaine caused a small, transient reduction in olfactory perception. The maximum reduction in olfactory perception (35%) was achieved by 60 mg lidocaine 15 min following administration, but perception could be increased to almost normal levels by increasing the odor stimulus dose. Detection of the lowest stimulus strength returned to normal levels after 30 min. CONCLUSIONS: Intranasal application of lidocaine, caused a reduction in olfactory perception, however, did not abolish the olfactory function 15 min following administration. Physiological/psychometric olfactory testing would not be precluded under these circumstances, and the effects of anesthesia could be overcome by increasing the stimulus strength.

The apoptotic effect of Zoledronic acid on the nasopharyngeal carcinoma cells via ROS mediated chloride channel activation.

Zoledronic acid (ZA), a third-generation bisphosphonate, has been applied for treatment of bone metastases caused by malignant tumors. Recent studies have found its anti-cancer effects on various tumor cells. One of the mechanisms of anti-cancer effects of ZA is induction of apoptosis. However, the mechanisms of ZA-induced apoptosis in tumor cells have not been clarified clearly. In this study, we investigated the roles of chloride channels in ZA-induced apoptosis in nasopharyngeal carcinoma CNE-2Z cells. Apoptosis and chloride current were induced by ZA and suppressed by chloride channel blockers. After the knockdown of ClC-3 expression by ClC-3 siRNA, ZA-induced chloride current and apoptosis were significantly suppressed, indicating that the chloride channel participated in ZA-induced apoptosis may be ClC-3. When reactive oxygen species (ROS) generation was inhibited by the antioxidant N-acetyl-L-cysteine (L-NAC), ZA-induced apoptosis and chloride current were blocked accordingly, suggesting that ZA induces apoptosis through promoting ROS production and subsequently activating chloride channel.

Estradiol activates chloride channels via estrogen receptor-α in the cell membranes of osteoblasts.

Estrogen plays important roles in regulation of bone formation. Cl- channels in the ClC family are expressed in osteoblasts and are associated with bone physiology and pathology, but the relationship between Cl- channels and estrogen is not clear. In this study the action of estrogen on Cl- channels was investigated in the MC3T3-E1 osteoblast cell line. Our results show that 17ß-estradiol could activate a current that reversed at a potential close to the Cl- equilibrium potential, with a sequence of anion selectivity of I- > Br- > Cl- > gluconate, and was inhibited by the Cl- channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoate and 4,4'-diisothiocyano-2,2'-stilbene disulfonic acid. Knockdown of ClC-3 Cl- channel expression by a specific small interfering RNA to ClC-3 attenuated activation of the 17ß-estradiol-induced Cl- current. Extracellular application of membrane-impermeable 17ß-estradiol-albumin conjugates activated a similar current. The estrogen-activated Cl- current could be inhibited by the estrogen receptor (ER) antagonist fulvestrant (ICI 182780). The selective ERα agonist, but not ERß agonist, activated a Cl- current similar to that induced by 17ß-estradiol. Silencing ERα expression prevented activation of estrogen-induced currents. Immunofluorescence and coimmunoprecipitation experiments demonstrated that ClC-3 Cl- channels and ERα were colocalized and closely related in cells. Estrogen promoted translocation of ClC-3 and ERα to the cell membrane from the nucleus. In conclusion, our findings show that Cl- channels can be activated by estrogen via ERα on the cell membrane and suggest that the ClC-3 Cl- channel may be one of the targets of estrogen in the regulation of osteoblast activity.

ClC-3 Chloride Channel Proteins Regulate the Cell Cycle by Up-regulating cyclin D1-CDK4/6 through Suppressing p21/p27 Expression in Nasopharyngeal Carcinoma Cells.

It was shown in this study that knockdown of ClC-3 expression by ClC-3 siRNA prevented the activation of hypotonicity-induced chloride currents, and arrested cells at the G0/G1 phase in nasopharyngeal carcinoma CNE-2Z cells. Reconstitution of ClC-3 expression with ClC-3 expression plasmids could rescue the cells from the cell cycle arrest caused by ClC-3 siRNA treatments. Transfection of cells with ClC-3 siRNA decreased the expression of cyclin D1, cyclin dependent kinase 4 and 6, and increased the expression of cyclin dependent kinase inhibitors (CDKIs), p21 and p27. Pretreatments of cells with p21 and p27 siRNAs depleted the inhibitory effects of ClC-3 siRNA on the expression of CDK4 and CDK6, but not on that of cyclin D1, indicating the requirement of p21 and p27 for the inhibitory effects of ClC-3 siRNA on CDK4 and CDK6 expression. ClC-3 siRNA inhibited cells to progress from the G1 phase to the S phase, but pretreatments of cells with p21 and p27 siRNAs abolished the inhibitory effects of ClC-3 siRNA on the cell cycle progress. Our data suggest that ClC-3 may regulate cell cycle transition between G0/G1 and S phases by up-regulation of the expression of CDK4 and CDK6 through suppression of p21 and p27 expression.

Combined non-adaptive light and smell stimuli lowered blood pressure, reduced heart rate and reduced negative affect.

Bright light therapy has been shown to have a positive impact on seasonal affective disorder (SAD), depression and anxiety. Smell has also has been shown to have effects on mood, stress, anxiety and depression. The objective of this study was to investigate the effect of the combination of light and smell in a non-adaptive cycle. Human subjects were given smell (lemon, lavender or peppermint) and light stimuli in a triangular wave (60scycle) for 15min. Blood pressure and heart rate were monitored before and after each session for 5 consecutive days and a Profile of Mood States (POMS) test was administered before and after the sensory stimulation on days 1, 3 and 5. The light-smell stimulus lowered blood pressure, both systolic and diastolic, and reduced heart rate for all odours compared to control. Of the two sensory stimuli, the odour stimulus contributed most to this effect. The different aromas in the light-smell combinations could be distinguished by their different effects on the mood factors with lemon inducing the greatest mood changes in Dejection-Depression, Anger-Hostility, Tension-Anxiety. In conclusion, combined light and smell stimulation was effective in lowering blood pressure, reducing heart rate and improving mood. The combination was more effective than either smell or light stimuli alone, suggesting that a light-smell combination would be a more robust and efficacious alternative treatment for depression, anxiety and stress.

Ethanol Promotes Cell Migration via Activation of Chloride Channels in Nasopharyngeal Carcinoma Cells.

BACKGROUND: Excessive alcohol consumption has been identified as a significant risk factor for cancer development. Chloride channels have been proved previously by us and others to be involved in cancer cell migration. However, it is unknown whether chloride channels are associated with the effects of ethanol (EtOH) on cancer cell activities. METHODS: The effects of EtOH on migration were detected by the wound healing assay in the nasopharyngeal carcinoma cells (CNE-2Z) and the normal nasopharyngeal epithelial cells (NP69-SV40T). The whole-cell patch clamp technique was used to record the EtOH-induced chloride current. The characteristics of the current were studied by anion substitution, hypertonic challenges, and channel blockers. RESULTS: EtOH promoted the migration of cancerous CNE-2Z cells, but could hardly affect the migration of normal NP69-SV40T cells. The EtOH-induced migration could be inhibited by the chloride channel blockers, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. The exposure of CNE-2Z cells to EtOH activated a chloride current, with the ion selectivity of I(-) >Br(-) > Cl(-) >gluconate, demonstrated by ion substitution experiments. EtOH could still activate a similar chloride current in the absence of Ca(2+) in the medium. The current could be inhibited by the hypertonicity-induced cell shrinkage and the channel blockers NPPB and tamoxifen. EtOH could also activate a chloride current in normal NP69-SV40T cells, with the properties similar to those in CNE-2Z cells, but the current density was much smaller than that recorded in cancerous CNE-2Z cells. CONCLUSIONS: It has been demonstrated in this study that EtOH can activate chloride channels and promote cell migration in cancerous cells, but can hardly affect the activities in normal cells. The data suggest for the first time that EtOH may promote cell migration via activation of chloride channels; long-term exposure to EtOH may increase the incident of tumor metastasis.

Effects and after-effects of chewing gum on vigilance, heart rate, EEG and mood.

Research has shown that chewing gum improves attention, although the mechanism for this effect remains unclear. This study investigated the effects and after-effects of chewing gum on vigilance, mood, heart rate and EEG. Participants completed a vigilance task four times; at baseline, with or without chewing gum, and twice post-chewing. EEG alpha and beta power at left frontal and temporal lobes, subjective mood and heart rate were assessed. Chewing gum shortened reaction time and increased the rate of hits, although hits fell during the second post-chewing task. Chewing gum heightened heart rate, but only during chewing. Gum also increased beta power at F7 and T3 immediately post-chewing, but not following the post-chewing tasks. The findings show that chewing gum affects several different indicators of alertness.

Burst firing versus synchrony in a gap junction connected olfactory bulb mitral cell network model.

A key player in olfactory processing is the olfactory bulb (OB) mitral cell (MC). We have used dual whole-cell patch-clamp recordings from the apical dendrite and cell soma of MCs to develop a passive compartmental model based on detailed morphological reconstructions of the same cells. Matching the model to traces recorded in experiments we find: C(m) = 1.91 ± 0.20 µF cm(-2), R(m) = 3547 ± 1934 Ω cm(2) and R(i) = 173 ± 99 Ω cm. We have constructed a six MC gap-junction (GJ) network model of morphologically accurate MCs. These passive parameters (PPs) were then incorporated into the model with Na(+), Kdr, and KA conductances and GJs from Migliore et al. (2005). The GJs were placed in the apical dendrite tuft (ADT) and their conductance adjusted to give a coupling ratio between MCs consistent with experimental findings (~0.04). Firing at ~50 Hz was induced in all six MCs with continuous current injections (0.05-0.07 nA) at 20 locations to the ADT of two of the MCs. It was found that MCs in the network synchronized better when they shared identical PPs rather than using their own PPs for the fit suggesting that the OB may have populations of MCs tuned for synchrony. The addition of calcium-activated potassium channels (iKCa) and L-type calcium channels (iCa(L)) (Bhalla and Bower, 1993) to the model enabled MCs to generate burst firing. However, the GJ coupling was no longer sufficient to synchronize firing. When cells were stimulated by a continuous current injection there was an initial period of asynchronous burst firing followed after ~120 ms by synchronous repetitive firing. This occurred as intracellular calcium fell due to reduced iCa(L) activity. The kinetics of one of the iCa(L) gate variables, which had a long activation time constant (τ ~ range 18-150 ms), was responsible for this fall in iCa(L). The model makes predictions about the nature of the kinetics of the calcium current that will need experimental verification.

ClC-3 is a main component of background chloride channels activated under isotonic conditions by autocrine ATP in nasopharyngeal carcinoma cells.

In this study, the activation mechanisms of the background chloride current and the role of the current in maintaining of basal cell volume were investigated in human nasopharyngeal carcinoma CNE-2Z cells. Under isotonic conditions, a background chloride current was recorded by the patch clamp technique. The current presented the properties similar to those of the volume-activated chloride current in the same cell line and was inhibited by chloride channel blockers or by cell shrinkage induced by hypertonic challenges. Extracellular applications of reactive blue 2, a purinergic receptor antagonist, suppressed the background chloride current in a concentration-dependent manner under isotonic conditions. Depletion of extracellular ATP with apyrase or inhibition of ATP release from cells by gadolinium chloride decreased the background current. Extracellular applications of micromolar concentrations of ATP activated a chloride current which was inhibited by chloride channel blockers and hypertonic solutions. Extracellular ATP could also reverse the action of gadolinium chloride. Transfection of CNE-2Z cells with ClC-3 siRNA knocked down expression of ClC-3 proteins, attenuated the background chloride current and prevented activation of the ATP-induced current. Furthermore, knockdown of ClC-3 expression or exposures of cells to ATP (10 mM), the chloride channel blockers 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen, or reactive blue 2 increased cell volume under isotonic conditions. The results suggest that ClC-3 protein may be a main component of background chloride channels which can be activated under isotonic conditions by autocrine/paracrine ATP through purinergic receptor pathways; the background current is involved in maintenance of basal cell volume.

Volume-activated chloride channels contribute to cell-cycle-dependent regulation of HeLa cell migration.

The activation of volume-activated chloride Cl(-) channels has been implicated to play important roles in modulating cell cycle and cell migration. The aim of this study was to determine whether volume-activated Cl(-) channels are involved in cell-cycle-dependent regulation of cell migration in HeLa cells. Using techniques including cell-cycle synchronization, transwell migration assays and the patch-clamp technique, we demonstrate in this study that both the expression of volume-activated chloride current (I(Cl,vol)) and the potential of cell migration are cell-cycle-dependent; specifically, these events were high in G(0)/G(1) phase, low in S phase, and medium in G(2)/M phase. Moreover, the mean density of I(Cl,vol) was positively correlated to the rate of cell migration during cell-cycle progression. Additionally, endogenous suppression of I(Cl,vol) by transfecting cells with ClC-3 antisense oligonucleotides arrested cells in S phase and slowed cell migration. Collectively, our results suggest that volume-activated Cl(-) channels contribute to the cell-cycle-dependent regulation of cell migration.

Suppression of ClC-3 channel expression reduces migration of nasopharyngeal carcinoma cells.

Recent studies suggest that chloride (Cl-) channels regulate tumor cell migration. In this report, we have used antisense oligonucleotides specific for ClC-3, the most likely molecular candidate for the volume-activated Cl- channel, to investigate the role of ClC-3 in the migration of nasopharyngeal carcinoma cells (CNE-2Z) in vitro. We found that suppression of ClC-3 expression inhibited the migration of CNE-2Z cells in a concentration-dependent manner. Whole-cell patch-clamp recordings and image analysis further demonstrated that ClC-3 suppression inhibited the volume-activated Cl- current (I(Cl,vol)) and regulatory volume decrease (RVD) of CNE-2Z cells. The expression of ClC-3 positively correlated with cell migration, I(Cl,vol) and RVD. These results strongly suggest that ClC-3 is a component or regulator of the volume-activated Cl- channel. ClC-3 may regulate CNE-2Z cell migration by modulating cell volume. ClC-3 may be a new target for cancer therapies.

Neuropharmacology of the olfactory bulb.

The olfactory bulb is located at the start of a hierarchical chain of sensory processing mechanisms. The relative ease of its isolation allows the possibility that models of these mechanisms might be integrated to develop a detailed understanding of function. In this sensory processing chain odour molecules evoke signal transduction in the olfactory receptor neurons. These signals represent the diverse range of molecular binding affinities of the olfactory receptor proteins. The first level of processing of this sensory input is performed by the neurons of the olfactory bulb. The olfactory system needs to filter the vast amount of sensory input it receives to be able to select the subset of biological significance. The importance of the olfactory bulb in this filtering process is suggested by its wide range of modulatory mechanisms. These mechanisms include an array of centrifugal inputs from other regions of the brain as well as numerous intrinsic feedback circuits. Given the complexity of the olfactory bulb and the range of its modulatory activity, the process of isolation of its components produces some difficulties of interpretation. This is mainly due to the removal of some of the effects of interaction and the change in balance that results. We present a summary of the current understanding of the interacting modulatory elements that are found in the olfactory bulb and a detailed account of the properties of mitral/tufted cells, the projection neurons of the olfactory bulb. This is followed by a discussion of the intrinsic and extrinsic modulatory systems acting on these cells. A consideration of the integration of the effects of these modulatory systems allows an understanding of how the output of the mitral/tufted cells is controlled. While significant progress has been made in the elucidation of the individual components as a result of advances in techniques over the last decade we suggest that there is a need for computational studies as a further aid to the understanding and interpretation of the weight of individual modulatory components in this dynamic interacting system.

Blockage of volume-activated chloride channels inhibits migration of nasopharyngeal carcinoma cells.

Cell migration is crucial for tumor metastasis. Membrane ion channels may play a major role in tumor cell migration because the cells must undergo changes in shape and volume during migration. In the present study, we used the transwell migration assay, an in vitro model for cell migration, and the patch-clamp technique to investigate the role of the volume-activated Cl(-) current (I(cl,vol)) in the regulation of the migration of nasopharyngeal carcinoma CNE-2Z cells. 5-Nitro-2- (3-phenylpropylamino) benzoic acid (NPPB) inhibited the I(cl,vol) and the migration of CNE-2Z cells with almost identical dose-dependent pattern (IC(50) of 98.1 microM and 97.7 microM for I(cl,vol) and cell migration, respectively). Extracellular adenosine triphosphate (ATP) also showed similar dose-dependent inhibitory effects on the currents and migration (IC(50) of 1.07mM, and 1.11mM for I(cl,vol) and cell migration, respectively). Hypotonic treatments, which activated I(cl,vol), increased cell migration. Exposure to hypertonic solutions, which was shown to suppress I(cl,vol), inhibited cell migration. Replacement of Cl(-) with gluconate, which is relatively chloride channel-impermeable, impaired cell migration, whereas substitution of Cl(-) by I(-) and Br(-), the chloride channel-permeable ions, did not significantly affect cell migration. Analysis of the effects of all the above treatments on I(cl,vol) and cell migration indicated that the inhibition of migration was positively correlated with the blockage of I(cl,vol), with a correlation coefficient (r) of 0.97, suggesting a functional relationship between I(cl,vol) and cell migration. These data suggest that the volume-activated Cl(-) channels are involved in cell migration.

Repetitive olfactory exposure to the biologically significant steroid androstadienone causes a hedonic shift and gender dimorphic changes in olfactory-evoked potentials.

The function of a sensory system is to transduce and relay sensory information in a constant and reproducible manner. However, in the olfactory processing of certain steroids this precept of sensory constancy does not appear to apply. Using threshold testing, psychometrics, and electrophysiological techniques, we investigated the effects of a repetitive exposure protocol on the response to androstadienone. Androstadienone is a steroid found in human secretions that has been widely proposed as a candidate for a human pheromone. The detection threshold, hedonic perception, and evoked potential response all changed following repetitive exposure to androstadienone and not to a control odorant, benzaldehyde. Furthermore, the exposure-dependent changes in evoked potentials exhibited a gender dimorphism in which there were changes in the later components of the evoked potentials specific to women. These components have been associated with cognitive and perceptual operations. This 'learning' to smell a compound found in sweat may be related to biological signaling.

A new method for measuring reaction times for odour detection at iso-intensity: Comparison between an unpleasant and pleasant odour.

A psychophysical detection test was developed to measure the reaction time of human subjects to a pleasant and an unpleasant odour. The response latencies to stimulation with a malodour (valeric acid) and pleasant odorant (amyl acetate) were compared over a range of different stimulus strengths. By expressing reaction time as a function of detection rate, the responses to the two odours can be compared at iso-intensity across the concentration range. This is the first study that allows odorants to be compared at the same intensity over a range of concentrations. The malodour valeric acid was detected more rapidly than amyl acetate; at the 50% detection level the reaction time for the detection of amyl acetate was 1.74 s compared 1.36 s for valeric acid (380 ms or 22% faster). Women were significantly faster than men at detecting both the unpleasant (by 18%) and pleasant (by 26%) odour at the 50% detection level and this disparity increased with decreasing stimulus strength. In conclusion, we demonstrate the ability of a new method for the measurement of reaction times to odour detection to discriminate between two different odours - a malodour and a non-malodour.

Changes in the odor quality of androstadienone during exposure-induced sensitization.

Androstadienone is a steroid found in human sweat and other secretions. It has been widely proposed as a candidate for a human pheromone. As an odorant it possesses some unique properties. Here we demonstrate that, firstly, there is a very wide range of thresholds in the human population, and they are not normally distributed. Secondly, repetitive exposure causes a decrease in detection threshold of more than four orders of magnitude, and thirdly, accompanying this sensitization process is a change in the perceived odor quality. Those with low to intermediate sensitivities ascribe to it a wide range of odor descriptors across the hedonic scale, but as these individuals become sensitized, their description changes to predominantly putrid. We propose that this change in odor quality reflects the presence of at least two receptor populations for androstadienone; a low-affinity receptor conveying pleasant odor qualities and a high-affinity receptor mediating unpleasant odor qualities. We further propose that repetitive exposure results in the increased expression of the high-affinity receptor thereby shifting the balance of perception to the negative end of the hedonic scale.

Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells.

The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5'-triphosphate (ATP), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of non-migrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relationship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells.

Activation of chloride current and decrease of cell volume by ATP in nasopharyngeal carcinoma cells.

Whole-cell patch clamp and cell volume measurement techniques were used to investigate the ATP-activated chloride current and the ATP effect on cell volume in nasopharyngeal carcinoma cells. Extracellular application of ATP in micromolar concentrations activated a current with the properties of modest outward rectification and negligible time-dependent inactivation in a dose-dependent manner. The current reversed at a potential [(-0.05+/-0.03) mV] close to the Cl- equilibrium potential (-0.9 mV). Substitution of Cl- with gluconate in the extracellular solution decreased the ATP-activated current and shifted the reversal potential positively. NPPB, one of the chloride channel blockers, inhibited the current by (81.03+/-9.36)%. The current was also depressed by the P2Y purinoceptor antagonist, reactive blue 2, by (67.39+/-5.06)%. ATP (50 micromol/L) decreased the cell volume under the isotonic condition. Depletion of extracellular and intracellular Cl- abolished the ATP effect on cell volume. The results suggest that extracellular ATP of micromolar scales can induce a chloride current associated with cell volume regulation by activation of chloride channel through binding to purinoceptor P2Y.