Carbachol induces oscillations in membrane potential and intracellular calcium in a colonic tumor cell line, HT-29

1997 ◽  
Vol 273 (4) ◽  
pp. C1186-C1193 ◽  
Author(s):  
P. Sand ◽  
T. Svenberg ◽  
B. Rydqvist

The patch-clamp technique was used to study the effects of carbachol (CCh) on HT-29 cells. During CCh exposure, the cells ( n = 23) depolarized close to the equilibrium potential for Cl−([Formula: see text]; −48 mV) and the membrane potential then started to oscillate (16/23 cells). In voltage-clamp experiments, similar oscillations in whole cell currents could be demonstrated. The whole cell conductance increased from 225 ± 25 pS in control solution to 6,728 ± 1,165 pS (means ± SE, n = 17). In substitution experiments (22 mM Cl− in bath solution,[Formula: see text]= 0 mV), the reversal potential changed from −41.6 ± 2.2 mV (means ± SE, n = 9) to −3.2 ± 2.0 mV (means ± SE, n = 7). When the cells were loaded with the calcium-sensitive fluorescent dye, fluo 3, and simultaneously patch clamped, CCh caused a synchronous oscillating pattern of fluorescence and membrane potential. In cell-attached patches, the CCh-activated currents reversed at a relative membrane potential of 1.9 ± 3.7 mV (means ± SE, n = 11) with control solution in the pipette and at 46.2 ± 5.3 mV (means ± SE, n = 10) with a 15 mM Cl− solution in the pipette. High K+ (144 mM) did not change the reversal potential significantly ( P ≤ 0.05, n = 8). In inside-out patches, calcium-dependent Cl−channels could be demonstrated with a conductance of 19 pS ( n = 7). It is concluded that CCh causes oscillations in membrane potential that involve calcium-dependent Cl−channels and a K+ permeability.

1993 ◽  
Vol 265 (6) ◽  
pp. C1501-C1510 ◽  
Author(s):  
B. Nilius ◽  
G. Schwarz ◽  
G. Droogmans

The modulation of intracellular calcium ([Ca2+]i) by the membrane potential was investigated in human melanoma cells by combining the nystatin-perforated patch-clamp technique with Ca2+ measurements. Voltage steps to -100 mV induced a rise in [Ca2+]i and a creeping inward current. These effects were absent in Ca(2+)-free solution and could be blocked by Ni2+ or La3+. Voltage ramps revealed a close correlation between [Ca2+]i and voltage, with the strongest voltage dependence around the resting potential. Long-lasting tail currents, closely correlated with the rise in [Ca2+]i and a reversal potential close to the K+ equilibrium potential, occurred if the membrane potential was clamped back to 0 mV. They were absent if intracellular K+ was replaced by Cs+ and blocked by extracellular tetraethylammonium (5 mM), Ba2+ (1 mM), or a membrane-permeable adenosine 3',5'-cyclic monophosphate analogue. These observations are discussed in relation to cell proliferation. The enhanced expression of K+ channels during cell proliferation provides a positive-feedback mechanism resulting in long-term changes in [Ca2+]i required for the G1-S transition in the cell cycle.


1994 ◽  
Vol 72 (6) ◽  
pp. 2903-2910 ◽  
Author(s):  
I. Araki

1. The actions of gamma-aminobutyric acid (GABA) on sacral parasympathetic preganglionic (SPP) neurons were examined in slice preparations using the whole cell patch-clamp technique. 2. Inhibitory postsynaptic currents (IPSCs), which were evoked by focal electrical stimulation, were recorded from SPP neurons in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a glutamate receptor antagonist. The IPSCs were substantially reduced by strychnine (1 microM), a glycine receptor antagonist. The remaining IPSCs were completely blocked by bicuculline (20 microM), a GABAA receptor antagonist. The mean peak amplitude of bicuculline-sensitive, GABAergic currents recorded at -60 mV was 53.6 +/- 10.9%, mean +/- SD (n = 8), of that of the total IPSCs. The GABAergic currents were reversed in polarity at about -30 mV, near the Cl- equilibrium potential. 3. GABA (5-50 microM) induced inward currents in SPP neurons with symmetrical internal and external Cl- concentrations. This response was completely blocked by 100 microM bicuculline. Muscimol (2-8 microM), a GABAA agonist, mimicked the GABA-induced responses, whereas a GABAB receptor agonist, baclofen (20-200 microM), produced responses in only a few cells. The GABA-induced currents reversed their polarity at approximately 0 mV, near the Cl- equilibrium potential. When the internal Cl- concentration was reduced, the reversal potential was shifted according to the Nernst equation for Cl-. 4. GABA-induced currents exhibited an outward "hump" between -35 and 15 mV. This voltage range coincided with that at which a depolarization-induced inward whole cell current was elicited.(ABSTRACT TRUNCATED AT 250 WORDS)


1996 ◽  
Vol 270 (6) ◽  
pp. G932-G938 ◽  
Author(s):  
J. Jury ◽  
K. R. Boev ◽  
E. E. Daniel

Single smooth muscle cells from the opossum body circular muscle were isolated and whole cell currents were characterized by the whole cell patch-clamp technique. When the cells were held at -50 mV and depolarized to 70 mV in 20-mV increments, initial small inactivating inward currents were evoked (-30 to 30 mV) followed by larger sustained outward currents. Depolarization from a holding potential of -90 mV evoked an initial fast inactivating outward current sensitive to 4-aminopyridine but not to high levels of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The outward currents reversed near K+ equilibrium potential and were abolished when KCl was replaced by CsCl in the pipette solution. The sustained outward current was inhibited by quinine and cesium. High EGTA in the pipette solution reduced but did not abolish the sustained outward currents, suggesting that both Ca(2+)-dependent and -independent currents were evoked. The nitric oxide (NO)-releasing agents Sin-1 and sodium nitroprusside increased outward K+ currents. High levels of EGTA in the pipette solution abolished the increase in outward current induced by Sin-1. The presence of cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum (SR) Ca2+ pump, blocked the effects of NO-releasing agents. We conclude that NO release activates K+ outward currents in opossum esophagus circular muscle, which may depend on Ca2+ release from the SR stores.


1991 ◽  
Vol 260 (5) ◽  
pp. C934-C948 ◽  
Author(s):  
K. Kusano ◽  
H. Gainer

Voltage- and Ca(2+)-activated whole cell currents were studied in AR42J cells, a clonal cell line derived from rat pancreatic acinar cells, using a patch electrode voltage-clamp technique. Four kinds of ionic currents were identified by their ionic dependencies, pharmacological properties, and kinetic parameters: 1) an outward current flow due mainly to a voltage-dependent K(+)-conductance increase, 2) an initial transient inward current due to an Na(+)-conductance increase, 3) transient and long-duration inward current due to a Ca(2+)-conductance increase, and 4) a slowly activating inward current that persists over the duration of the depolarizing pulse and deactivates slowly upon repolarization, producing a slow inward tail current. The slow inward tail current was particularly robust and was interpreted as due to a Ca(2+)-activated Cl(-)-conductance increase, since 1) the generation of this current was blocked by removing the extracellular Ca2+, applying Ca(2+)-channel blockers (Cd2+, nifedipine), or by lowering the intracellular Ca2+ concentration [( Ca2+]i) with EGTA; and 2) the reversal potential (Erev) of the slow inward tail current was close to 0 mV in the control condition (152 mM [Cl-]o/154 mM [Cl-]i), and changes of the [Cl-]o/[Cl )i ratio shifted the Erev toward the predicted Cl- equilibrium potential.


2000 ◽  
Vol 84 (3) ◽  
pp. 1681-1691 ◽  
Author(s):  
Werner Kilb ◽  
Heiko J. Luhmann

Cajal-Retzius cells are among the first neurons appearing during corticogenesis and play an important role in the establishment of cortical lamination. To characterize the hyperpolarization-activated inward current ( I h) and to investigate whether I h contributes to the relatively positive resting membrane potential (RMP) of these cells, we analyzed the properties of I h in visually identified Cajal-Retzius cells in cortical slices from neonatal rats using the whole cell patch-clamp technique. Membrane hyperpolarization to −90 mV activated a prominent inward current that was inhibited by 1 mM Cs+ and was insensitive to 1 mM Ba2+. The activation time constant for I h was strongly voltage dependent. In Na+-free solution, I h was reduced, indicating a contribution of Na+. An analysis of the tail currents revealed a reversal potential of −45.2 mV, corresponding to a permeability coefficient (pNa+/pK+) of 0.13. While an increase in the extracellular K+ concentration ([K+]e) enhances I h, it was reduced by a [K+]e decrease. This [K+]e dependence could not be explained by an effect on the electromotive force on K+ but suggested an additional extracellular binding site for K+ with an apparent dissociation constant of 7.2 mM. Complete Cl−substitution by Br−, I−, or NO3 − had no significant effect on I h, whereas a complete Cl−substitution by the organic compounds methylsulfate, isethionate, or gluconate reduced I h by ∼40%. The I h reduction observed in gluconate could be abolished by the addition of Cl−. The analysis of the [Cl−]e dependence of I h revealed a dissociation constant of 9.8 mM and a Hill-coefficient of 2.5, while the assumption of a gluconate-dependent I h reduction required an unreasonably high Hill-coefficient >20. An internal perfusion with the lidocaine derivative lidocaine N-ethyl bromide blocks I h within 1 min after establishment of the whole cell configuration. An inhibition of I h by 1 mM Cs+ was without an effect on RMP, action potential amplitude, threshold, width, or afterhyperpolarization. We conclude from these results that Cajal-Retzius cells express a prominent I hwith characteristic properties that does not contribute to the RMP.


2003 ◽  
Vol 284 (4) ◽  
pp. C839-C847 ◽  
Author(s):  
Sok Han Kang ◽  
Pieter Vanden Berghe ◽  
Terence K. Smith

Whole cell patch-clamp recordings were made from cultured myenteric neurons taken from murine proximal colon. The micropipette contained Cs+ to remove K+ currents. Depolarization elicited a slowly activating time-dependent outward current ( I tdo), whereas repolarization was followed by a slowly deactivating tail current ( I tail). I tdo and I tail were present in ∼70% of neurons. We identified these currents as Cl− currents ( I Cl), because changing the transmembrane Cl− gradient altered the measured reversal potential ( E rev) of both I tdo and I tail with that for I tailshifted close to the calculated Cl− equilibrium potential ( E Cl). I Cl are Ca2+-activated Cl− current [ I Cl(Ca)] because they were Ca2+dependent. E Cl, which was measured from the E rev of I Cl(Ca) using a gramicidin perforated patch, was −33 mV. This value is more positive than the resting membrane potential (−56.3 ± 2.7 mV), suggesting myenteric neurons accumulate intracellular Cl−. ω-Conotoxin GIVA [0.3 μM; N-type Ca2+ channel blocker] and niflumic acid [10 μM; known I Cl(Ca) blocker], decreased the I Cl(Ca). In conclusion, these neurons have I Cl(Ca) that are activated by Ca2+entry through N-type Ca2+ channels. These currents likely regulate postspike frequency adaptation.


1986 ◽  
Vol 251 (1) ◽  
pp. C85-C89 ◽  
Author(s):  
N. W. Richards ◽  
D. C. Dawson

The patch-clamp technique for recording single-channel currents across cell membranes was applied to single turtle colon epithelial cells isolated with hyaluronidase. With electrodes fabricated from Corning #7052 glass, high-resistance seals were consistently formed to these cells. In on-cell patches with low K (2.5 mM) in the pipette and high K (114.5 mM) in the bath, outward K currents were recorded that had a slope conductance of 17 pS and a reversal potential greater than -70 mV. Currents through this K channel were blocked by lidocaine, quinidine, and barium. These agents also block a cell swelling-induced K conductance identified by macroscopic current measurements in the basolateral membranes of the intact colonic epithelium, suggesting that the 17 pS K channel identified by single-channel recording in isolated turtle colon cells may be responsible for this macroscopically defined K conductance.


1999 ◽  
Vol 114 (6) ◽  
pp. 771-786 ◽  
Author(s):  
Lydia M. Henderson ◽  
Robert W. Meech

Expression of gp91-phox in Chinese hamster ovary (CHO91) cells is correlated with the presence of a voltage-gated H+ conductance. As one component of NADPH oxidase in neutrophils, gp91-phox is responsible for catalyzing the production of superoxide (O2·2). Suspensions of CHO91 cells exhibit arachidonate-activatable H+ fluxes (Henderson, L.M., G. Banting, and J.B. Chappell. 1995. J. Biol. Chem. 270:5909–5916) and we now characterize the electrical properties of the pathway. Voltage-gated currents were recorded from CHO91 cells using the whole-cell configuration of the patch-clamp technique under conditions designed to exclude a contribution from ions other than H+. As in other voltage-gated proton currents (Byerly, L., R. Meech, and W. Moody. 1984. J. Physiol. 351:199–216; DeCoursey, T.E., and V.V. Cherny. 1993. Biophys. J. 65:1590–1598), a lowered external pH (pHo) shifted activation to more positive voltages and caused the tail current reversal potential to shift in the manner predicted by the Nernst equation. The outward currents were also reversibly inhibited by 200 μM zinc. Voltage-gated currents were not present immediately upon perforating the cell membrane, but showed a progressive increase over the first 10–20 min of the recording period. This time course was consistent with a gradual shift in activation to more negative potentials as the pipette solution, pH 6.5, equilibrated with the cell contents (reported by Lucifer yellow included in the patch pipette). Use of the pH-sensitive dye 2′7′ bis-(2-carboxyethyl)-5(and 6) carboxyfluorescein (BCECF) suggested that the final intracellular pH (pHi) was ∼6.9, as though pHi was largely determined by endogenous cellular regulation. Arachidonate (20 μM) increased the amplitude of the currents by shifting activation to more negative voltages and by increasing the maximally available conductance. Changes in external Cl− concentration had no effect on either the time scale or the appearance of the currents. Examination of whole cell currents from cells expressing mutated versions of gp91-phox suggest that: (a) voltage as well as arachidonate sensitivity was retained by cells with only the NH2-terminal 230 amino acids, (b) histidine residues at positions 111, 115, and 119 on a putative membrane-spanning helical region of the protein contribute to H+ permeation, (c) histidine residues at positions 111 and 119 may contribute to voltage gating, (d) the histidine residue at position 115 is functionally important for H+ selectivity. Mechanisms of H+ permeation through gp91-phox include the possible protonation/deprotonation of His-115 as it is exposed alternatively to the interior and exterior faces of the cell membrane (see Starace, D.M., E. Stefani, and F. Bezanilla. 1997. Neuron. 19:1319–1327) and the transfer of protons across an “H-X-X-X-H-X-X-X-H” motif lining a conducting pore.


1998 ◽  
Vol 45 (2) ◽  
pp. 311-326 ◽  
Author(s):  
A Ayar ◽  
N M Thatcher ◽  
U Zehavi ◽  
D R Trentham ◽  
R H Scott

The ability of dihydrosphingosine to release Ca2+ from intracellular stores in neurones was investigated by combining the whole cell patch clamp technique with intracellular flash photolysis of caged, N-(2-nitrobenzyl)dihydrosphingosine. The caged dihydrosphingosine (100 microM) was applied to the intracellular environment via the CsCl-based patch pipette solution which also contained 0.3% dimethylformamide and 2 mM dithiothreitol. Cultured dorsal root ganglion neurones from neonatal rats were voltage clamped at -90 mV and inward whole cell Ca2+-activated currents were recorded in response to intracellular photorelease of dihydrosphingosine. Intracellular photorelease of dihydrosphingosine (about 5 microM) was achieved using a Xenon flash lamp. Inward Ca2+-activated currents were evoked in 50 out of 57 neurones, the mean delay to current activation following photolysis was 82+/-13 s. The responses were variable with neurones showing transient, oscillating or sustained inward currents. High voltage-activated Ca2+ currents evoked by 100 ms voltage step commands to 0 mV were not attenuated by photorelease of dihydrosphingosine. Controls showed that alone a flash from the Xenon lamp did not activate currents, and that the unphotolysed caged dihydrosphingosine, and intracellular photolysis of 2-(2-nitrobenzylamino) propanediol also did not evoke responses. The dihydrosphingosine current had a reversal potential of -11+/-3 mV (n = 11), and was carried by two distinct Cl- and cation currents which were reduced by 85% and about 20% following replacement of monovalent cations with N-methyl-D-glucamine or application of the Cl- channel blocker niflumic acid (10 microM) respectively. The responses to photoreleased dihydrosphingosine were inhibited by intracellular application of 20 mM EGTA, 10 microM ryanodine or extracellular application of 10 microM dantrolene, but persisted when Ca2+ free saline was applied to the extracellular environment. Intracellular application of uncaged dihydrosphingosine evoked responses which were attenuated by photolysis of the caged Ca2+ chelator Diazo-2. Experiments also suggested that extracellular application of dihydrosphingosine can activate membrane conductances. We conclude that dihydrosphingosine directly or indirectly mobilises Ca2+ from ryanodine-sensitive intracellular stores in cultured sensory neurones.


2020 ◽  
Author(s):  
Elis Torrezan-Nitao ◽  
Sean G Brown ◽  
Esperanza Mata-Martínez ◽  
Claudia L Treviño ◽  
Christopher Barratt ◽  
...  

Abstract STUDY QUESTION How are progesterone (P4)-induced repetitive intracellular Ca2+ concentration ([Ca2+]i) signals (oscillations) in human sperm generated? SUMMARY ANSWER P4-induced [Ca2+]i oscillations are generated in the flagellum by membrane potential (Vm)-sensitive Ca2+-influx through CatSper channels. WHAT IS KNOWN ALREADY A subset of human sperm display [Ca2+]i oscillations that regulate flagellar beating and acrosome reaction. Although pharmacological manipulations indicate involvement of stored Ca2+ in these oscillations, influx of extracellular Ca2+ is also required. STUDY DESIGN, SIZE, DURATION This was a laboratory study that used >20 sperm donors and involved more than 100 separate experiments and analysis of more than 1000 individual cells over a period of 2 years. PARTICIPANTS/MATERIALS, SETTING, METHODS Semen donors and patients were recruited in accordance with local ethics approval from Birmingham University and Tayside ethics committees. [Ca2+]i responses and Vm of individual cells were examined by fluorescence imaging and whole-cell current clamp. MAIN RESULTS AND THE ROLE OF CHANCE P4-induced [Ca2+]i oscillations originated in the flagellum, spreading to the neck and head (latency of 1–2 s). K+-ionophore valinomycin (1 µM) was used to investigate the role of membrane potential (Vm). Direct assessment by whole-cell current-clamp confirmed that Vm in valinomycin-exposed cells was determined primarily by K+ equilibrium potential (EK) and was rapidly ‘reset’ upon manipulation of [K+]o. Pre-treatment of sperm with valinomycin ([K+]o = 5.4 mM) had no effect on the P4-induced [Ca2+] transient (P = 0.95; eight experiments), but application of valinomycin to P4-pretreated sperm suppressed activity in 82% of oscillating cells (n = 257; P = 5 × 10−55 compared to control) and significantly reduced both the amplitude and frequency of persisting oscillations (P = 0.0001). Upon valinomycin washout, oscillations re-started in most cells. When valinomycin was applied in saline with elevated [K+], the inhibitory effect of valinomycin was reduced and was dependent on EK (P = 10−25). Amplitude and frequency of [Ca2+]i oscillations that persisted in the presence of valinomycin showed similar sensitivity to EK (P < 0.01). The CatSper inhibitor RU1968 (4.8 and 11 µM) caused immediate and reversible arrest of activity in 36% and 96% of oscillating cells, respectively (P < 10−10). Quinidine (300 µM) which blocks the sperm K+ current (IKsper) completely, inhibited [Ca2+]i oscillations. LARGE SCALE DATA N/A LIMITATIONS, REASONS FOR CAUTION This was an in-vitro study and caution must be taken when extrapolating these results to in-vivo regulation of sperm. WIDER IMPLICATIONS OF THE FINDINGS [Ca2+]i oscillations in human sperm are functionally important and their absence is associated with failed fertilisation at IVF. The data reported here provide new understanding of the mechanisms that underlie the regulation and generation (or failure) of these oscillations. STUDY FUNDING/COMPETING INTEREST(S) E.T.-N. was in receipt of a postgraduate scholarship from the CAPES Foundation (Ministry of Education, Brazil). E.M-M received travel funds from the Programa de Apoyo a los Estudios de Posgrado (Maestria y Doctorado en Ciencias Bioquimicas-Universidad Autonoma de Mexico). SGB and CLRB are recipients of a Chief Scientist Office (NHS Scotland) grant TCS/17/28. The authors have no conflicts of interest.


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