Voltage-dependent kinetics of Na-Ca exchange current in Ca(2+)-loaded guinea pig heart cells

1993 ◽  
Vol 265 (5) ◽  
pp. C1258-C1265 ◽  
Author(s):  
K. Benndorf ◽  
C. Biskup ◽  
M. Friedrich
Keyword(s):  
Guinea Pig ◽  
Time Course ◽  
Exchange Current ◽  
Heart Cells ◽  
Current Component ◽  
Patch Clamp Technique ◽  
Initial Current ◽  
Current Increase ◽  
Voltage Dependent ◽  
Kinetics Of

Voltage-dependent properties of Na-Ca exchange current were revealed with the patch-clamp technique in Ca(2+)-overloaded guinea pig ventricular myocytes in the whole cell configuration. With the assumption that the transient inward current (Iti) is mediated by the Na-Ca exchanger, oscillations of internal Ca2+ concentration ([Ca2+]i) were used to investigate voltage-dependent kinetics of exchange current differences at two [Ca2+]i values. After Iti was elicited by clamping from -45 mV to basic pulses of +10 mV, pairs of equipotential short test pulses were applied during the basic pulse at both the phase of low [Ca2+]i (between two neighboring Iti values) and the phase of high [Ca2+]i (at the peak of Iti). The test pulses were short enough to leave the time course of Iti during the basic pulse approximately unchanged, which allowed study of the voltage dependence of the respective current differences without disturbing the underlying oscillation of [Ca2+]i. The current differences were inward at all potentials between -140 and +70 mV, started from an equal initial value, and obeyed characteristic voltage-dependent time courses: hyperpolarization to potentials negative to -70 mV caused an initial current increase, which was followed by a decay to very small amplitudes or zero with a decay time constant decreasing toward hyperpolarization e-fold per 45.6 mV. Depolarizing pulses caused a decay of the current differences to smaller levels. Respective current differences formed during a slowly decaying current component, following the Ca current spike, showed equal voltage-dependent properties. This indicates that the slowly decaying current component is preferentially also carried by the Na-Ca exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)

Voltage-dependent calcium channel current in isolated gallbladder smooth muscle cells of guinea pig

1993 ◽  
Vol 264 (6) ◽  
pp. G1066-G1076 ◽  
Author(s):  
T. Shimada
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Time Course ◽  
Reversal Potential ◽  
High Sensitivity ◽  
Muscle Cells ◽  
Patch Clamp Technique ◽  
Decay Component ◽  
Voltage Dependent

The voltage-dependent Ca2+ current was studied in enzymatically dispersed guinea pig gallbladder smooth muscle cells using the whole cell patch-clamp technique. Depolarizing voltage (V) steps induced an inward current (I) that was carried by Ca2+. The threshold potential was -40 to -30 mV, the maximal current was observed at +10 to +20 mV, and the reversal potential was around +80 mV. I-V curves obtained with holding potentials of -80 and -40 mV were not significantly different. This current had a high sensitivity to dihydropyridine drugs, and the Ba2+ or Sr2+ current was larger than the Ca2+ current. Activation was accelerated by increasing the membrane potential. In general, the time course of decay was well fitted by the sum of two exponentials, but consideration of a third (ultra-slow) decay component was also necessary when the current generated by a 2-s command pulse was analyzed. Superimposition of activation and inactivation curves showed the presence of a significant window current. Carbachol suppressed the Ca2+ current only when the pipette contained a low concentration of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. These results show that the L-type Ca2+ current is dominant in gallbladder smooth muscle cells and may contribute to excitation-contraction coupling.

Voltage-dependent K+ current in capillary endothelial cells isolated from guinea pig heart

1999 ◽  
Vol 277 (1) ◽  
pp. H119-H127 ◽  
Author(s):  
Michael Dittrich ◽  
Jürgen Daut
Keyword(s):  
Guinea Pig ◽  
Time Course ◽  
Single Channel ◽  
Patch Clamp Technique ◽  
Guinea Pig Heart ◽  
Potential Oscillations ◽  
Time To Peak ◽  
Voltage Dependent ◽  
Capillary Endothelial Cells ◽  
Single Channel Currents

Capillary fragments were isolated from guinea pig hearts, and their electrical properties were studied using the perforated-patch and cell-attached mode of the patch-clamp technique. A voltage-dependent K+ current was discovered that was activated at potentials positive to −20 mV and showed a sigmoid rising phase. For depolarizing voltage steps from −128 to +52 mV, the time to peak was 71 ± 5 ms (mean ± SE) and the amplitude of the current was 3.7 ± 0.5 pA/pF in the presence of 5 mM external K+. The time course of inactivation was exponential with a time constant of 7.2 ± 0.5 s at +52 mV. The current was blocked by tetraethylammonium (inhibitory constant ∼3 mM) but was not affected by charybdotoxin (1 μM) or apamin (1 μM). In the cell-attached mode, depolarization-activated single-channel currents were found that inactivated completely within 30 s; the single-channel conductance was 12.3 ± 2.4 pS. The depolarization-activated K+current described here may play a role in membrane potential oscillations of the endothelium.

Preferential potentiation by hypotonic cell swelling of muscarinic cation current in guinea pig ileum

1997 ◽  
Vol 272 (1) ◽  
pp. C240-C253 ◽  
Author(s):  
Y. Waniishi ◽  
R. Inoue ◽  
Y. Ito
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Muscarinic Receptor ◽  
Time Course ◽  
Cell Swelling ◽  
Patch Clamp Technique ◽  
Cationic Current ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Hypotonic Cell Swelling

The effects of hypotonic cell swelling (HCS) on muscarinic receptor-activated cationic current in guinea pig ileal smooth muscle were investigated by the whole cell patch-clamp technique. With nystatin-perforated recording, reduced external tonicity from 312 to 262 mosM caused cell swelling but hardly affected the membrane currents activated by depolarization, such as outward-rectifying K and voltage-dependent Ca currents. In contrast, the inward current evoked by carbachol at -60 mV was greatly increased (approximately 50%) by the same extent of hypotonicity. This effect is likely to occur through potentiation of nonselective cation channels coupled to the muscarinic receptor (mNSCCs) and probably does not involve elevated intracellular Ca2+ concentration ([Ca2+]i), since neither removal of external Ca2+ nor [Ca2+]i buffering with 10 mM 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid significantly affected the results. Furthermore, the time course and degree of this potentiation closely matched those of video-microscopically monitored HCS. These results support the view that mechanosensitive modulation may be a powerful mechanism to regulate mNSCCs activity in gut smooth muscle, together with membrane potential and [Ca2+]i.

Force measurements from voltage-clamped guinea pig ventricular myocytes

1990 ◽  
Vol 258 (2) ◽  
pp. H452-H459 ◽  
Author(s):  
N. Shepherd ◽  
M. Vornanen ◽  
G. Isenberg
Keyword(s):  
Guinea Pig ◽  
Time Course ◽  
Ventricular Myocytes ◽  
Isometric Force ◽  
Contractile Force ◽  
Patch Clamp Technique ◽  
Thin Glass ◽  
Tonic Component ◽  
Time To Peak ◽  
Whole Cell Patch Clamp

We describe the first observations of isolated mammalian guinea pig ventricular myocytes that combine measurements of contractile force with the voltage-clamp method. The myocytes were attached by poly-L-lysine to the beveled ends of a pair of thin glass rods having a compliance of 0.76 m/N. The contractile force of a cell caused a 1- to 3-microm displacement of the rods; the motion of which was converted to an output voltage by phototransistors. By the use of the whole cell patch-clamp technique, the cells were depolarized at 1 Hz with 200-ms-long clamp pulses from -45 to +5 mV (35 degrees C, 3.6 mM CaCl2). Isometric force began after a latency of 7 +/- 2 ms, peaked at 93 +/- 21 ms, and relaxed (90%) at 235 +/- 63 ms. The time course of force was always faster than that of isotonic shortening (time to peak 154 +/- 18 ms). With 400-ms-long depolarizations, a tonic component was recorded as either sustained force or sustained shortening that decayed on repolarization. Substitution of Ca by Sr in the bath increased the inward current through Ca channels but slowed down the time course of force development. The results are consistent with the hypothesis that activator calcium derives mainly from internal stores and that Ca release needs Ca entry through channels.

Two types of voltage-dependent potassium channels in outer hair cells from the guinea pig cochlea

1999 ◽  
Vol 277 (5) ◽  
pp. C913-C925 ◽  
Author(s):  
Thierry van den Abbeele ◽  
Jacques Teulon ◽  
Patrice Tran Ba Huy
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Basolateral Membrane ◽  
Outer Hair Cells ◽  
Catalytic Subunit ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Guinea Pig Cochlea ◽  
Voltage Dependent ◽  
Inside Out

Cell-attached and cell-free configurations of the patch-clamp technique were used to investigate the conductive properties and regulation of the major K+channels in the basolateral membrane of outer hair cells freshly isolated from the guinea pig cochlea. There were two major voltage-dependent K+ channels. A Ca2+-activated K+ channel with a high conductance (220 pS, P K/ P Na= 8) was found in almost 20% of the patches. The inside-out activity of the channel was increased by depolarizations above 0 mV and increasing the intracellular Ca2+concentration. External ATP or adenosine did not alter the cell-attached activity of the channel. The open probability of the excised channel remained stable for several minutes without rundown and was not altered by the catalytic subunit of protein kinase A (PKA) applied internally. The most frequent K+ channel had a low conductance and a small outward rectification in symmetrical K+ conditions (10 pS for inward currents and 20 pS for outward currents, P K/ P Na= 28). It was found significantly more frequently in cell-attached and inside-out patches when the pipette contained 100 μM acetylcholine. It was not sensitive to internal Ca2+, was inhibited by 4-aminopyridine, was activated by depolarization above −30 mV, and exhibited a rundown after excision. It also had a slow inactivation on ensemble-averaged sweeps in response to depolarizing pulses. The cell-attached activity of the channel was increased when adenosine was superfused outside the pipette. This effect also occurred with permeant analogs of cAMP and internally applied catalytic subunit of PKA. Both channels could control the cell membrane voltage of outer hair cells.

ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization

2002 ◽  
Vol 283 (4) ◽  
pp. G1004-G1013 ◽  
Author(s):  
Marcelo Catalán ◽  
Isabel Cornejo ◽  
Carlos D. Figueroa ◽  
María Isabel Niemeyer ◽  
Francisco V. Sepúlveda ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Guinea Pig ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Surface Epithelium ◽  
Patch Clamp Technique ◽  
Chloride Currents ◽  
Kinetics Of

The principal function of the colon in fluid homeostasis is the absorption of NaCl and water. Apical membrane Na+ channels, Na+/H+ and Cl−/HCO[Formula: see text] exchangers, have all been postulated to mediate NaCl entry into colonocytes. The identity of the basolateral exit pathway for Cl− is unknown. We have previously demonstrated the presence of the ClC-2 transcript in the guinea pig intestine. Now we explore in more detail, the tissue and cellular distribution of chloride channel ClC-2 in the distal colon by in situ hybridization and immunohistochemistry. The patch-clamp technique was used to characterize Cl− currents in isolated surface epithelial cells from guinea pig distal colon and these were compared with those mediated by recombinant guinea pig (gp)ClC-2. ClC-2 mRNA and protein were found in the surface epithelium of the distal colon. Immunolocalization revealed that, in addition to some intracellular labeling, ClC-2 was present in the basolateral membranes but absent from the apical pole of colonocytes. Isolated surface epithelial cells exhibited hyperpolarization-activated chloride currents showing a Cl− > I− permeability and Cd2+ sensitivity. These characteristics, as well as some details of the kinetics of activation and deactivation, were very similar to those of recombinant gpClC-2 measured in parallel experiments. The presence of active ClC-2 type currents in surface colonic epithelium, coupled to a basolateral location for ClC-2 in the distal colon, suggests a role for ClC-2 channel in mediating basolateral membrane exit of Cl− as an essential step in a NaCl absorption process.

scholarly journals A time- and voltage-dependent K+ current in single cardiac cells from bullfrog atrium.

1986 ◽  
Vol 88 (6) ◽  
pp. 777-798 ◽  
Author(s):  
J R Hume ◽  
W Giles ◽  
K Robinson ◽  
E F Shibata ◽  
R D Nathan ◽  
...  
Keyword(s):  
Time Course ◽  
Voltage Dependence ◽  
Outward Current ◽  
Cardiac Cells ◽  
Delayed Rectifier ◽  
Mechanical Dispersion ◽  
Atrial Cells ◽  
Voltage Dependent ◽  
K Current ◽  
Kinetics Of

Individual myocytes were isolated from bullfrog atrium by enzymatic and mechanical dispersion, and a one-microelectrode voltage clamp was used to record the slow outward K+ currents. In normal [K+]o (2.5 mM), the slow outward current tails reverse between -95 and -100 mV. This finding, and the observed 51-mV shift of Erev/10-fold change in [K+]o, strongly suggest that the "delayed rectifier" in bullfrog atrial cells is a K+ current. This current, IK, plays an important role in initiating repolarization, and it is distinct from the quasi-instantaneous, inwardly rectifying background current, IK. In atrial cells, IK does not exhibit inactivation, and very long depolarizing clamp steps (20 s) can be applied without producing extracellular K+ accumulation. The possibility of [K+]o accumulation contributing to these slow outward current changes was assessed by (a) comparing reversal potentials measured after short (2 s) and very long (15 s) activating prepulses, and (b) studying the kinetics of IK at various holding potentials and after systematically altering [K+]o. In the absence of [K+]o accumulation, the steady state activation curve (n infinity) and fully activated current-voltage (I-V) relation can be obtained directly. The threshold of the n infinity curve is near -50 mV, and it approaches a maximum at +20 mV; the half-activation point is approximately -16 mV. The fully activated I-V curve of IK is approximately linear in the range -40 to +30 mV. Semilog plots of the current tails show that each tail is a single-exponential function, which suggests that only one Hodgkin-Huxley conductance underlies this slow outward current. Quantitative analysis of the time course of onset of IK and of the corresponding envelope of tails demonstrate that the activation variable, n, must be raised to the second power to fit the sigmoid onset accurately. The voltage dependence of the kinetics of IK was studied by recording and curve-fitting activating and deactivating (tail) currents. The resulting 1/tau n curve is U-shaped and somewhat asymmetric; IK exhibits strong voltage dependence in the diastolic range of potentials. Changes in the [Ca2+]o in the superfusing Ringer's, and/or addition of La3+ to block the transmembrane Ca2+ current, show that the time course and magnitude of IK are not significantly modulated by transmembrane Ca2+ movements, i.e., by ICa. These experimentally measured voltage- and time-dependent descriptors of IK strongly suggest an important functional role for IK in atrial tissue: it initiates repolarization and can be an important determinant of rate-induced changes in action potential duration.

scholarly journals Outward current in single smooth muscle cells of the guinea pig taenia coli.

1989 ◽  
Vol 93 (3) ◽  
pp. 551-564 ◽  
Author(s):  
Y Yamamoto ◽  
S L Hu ◽  
C Y Kao
Keyword(s):  
Guinea Pig ◽  
Time Constant ◽  
Time Course ◽  
Reversal Potential ◽  
Outward Current ◽  
Enzymatic Digestion ◽  
Taenia Coli ◽  
Physiological Conditions ◽  
Dependent Component ◽  
Voltage Dependent

In single myocytes of the guinea pig taenia coli, dispersed by enzymatic digestion, the late outward current is carried by K+. It has both a Ca2+-activated component and a voltage-dependent component which is resistant to external Co2+. The reversal potential is -84 mV, and the channel(s) for it are highly selective to K+. At 33 degrees C, the activation follows n2 kinetics, with a voltage-dependent time constant of 10.6 ms at 0 mV, which shortens to 1.7 ms at +70 mV. Deactivation follows a single-exponential time course, with a voltage-dependent time constant of 11 ms at -50 mV, which lengthens to 33 ms at -20 mV. During a 4.5-s maintained depolarization, IK inactivates, most of it into two exponential components, but there is a small noninactivating residue. It is surmised that during an action potential under physiological conditions, there is sufficient IK to cause repolarization.

scholarly journals Shaker potassium channel gating. I: Transitions near the open state.

1994 ◽  
Vol 103 (2) ◽  
pp. 249-278 ◽  
Author(s):  
T Hoshi ◽  
W N Zagotta ◽  
R W Aldrich
Keyword(s):  
Time Course ◽  
Single Channel ◽  
Activation Process ◽  
Time Data ◽  
Shaker Potassium Channel ◽  
Voltage Dependent ◽  
Average Current ◽  
Shaker Potassium Channels ◽  
Kinetics Of ◽  
Deactivation Process

Kinetics of single voltage-dependent Shaker potassium channels expressed in Xenopus oocytes were studied in the absence of fast N-type inactivation. Comparison of the single-channel first latency distribution and the time course of the ensemble average current showed that the activation time course and its voltage dependence are largely determined by the transitions before first opening. The open dwell time data are consistent with a single kinetically distinguishable open state. Once the channel opens, it can enter at least two closed states which are not traversed frequently during the activation process. The rate constants for the transitions among these closed states and the open state are nearly voltage-independent at depolarized voltages (> -30 mV). During the deactivation process at more negative voltages, the channel can close directly to a closed state in the activation pathway in a voltage-dependent fashion.

scholarly journals Regulation kinetics of Na + ‐Ca 2+ exchange current in guinea‐pig ventricular myocytes

2000 ◽  
Vol 529 (3) ◽  
pp. 611-623 ◽  
Author(s):  
Yasutada Fujioka ◽  
Koh Hiroe ◽  
Satoshi Matsuoka
Keyword(s):  
Guinea Pig ◽  
Ventricular Myocytes ◽  
Exchange Current ◽  
Kinetics Of
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