scholarly journals Voltage-dependent decrease in the availability of single calcium channels by nitrendipine in guinea-pig ventricular cells.

1988 ◽  
Vol 402 (1) ◽  
pp. 219-235 ◽  
Author(s):  
Y Kawashima ◽  
R Ochi
Keyword(s):  
Guinea Pig ◽  
Calcium Channels ◽  
Ventricular Cells ◽  
Voltage Dependent ◽  
Single Calcium Channels

Single calcium channels in resistance-sized cerebral arteries from rats

1993 ◽  
Vol 264 (2) ◽  
pp. H470-H478 ◽  
Author(s):  
J. M. Quayle ◽  
J. G. McCarron ◽  
J. R. Asbury ◽  
M. T. Nelson
Keyword(s):  
Steady State ◽  
Calcium Channels ◽  
Single Channel ◽  
Cerebral Arteries ◽  
Membrane Depolarization ◽  
Barium Concentration ◽  
Voltage Dependent ◽  
Steady State Inactivation ◽  
Wistar Kyoto ◽  
Single Calcium Channels

Unitary currents through single calcium channels were measured from cell-attached patches on smooth muscle cells isolated from resistance-sized branches of posterior cerebral arteries from Wistar-Kyoto normotensive rats. Barium (80 and 10 mM) was used as the charge carrier, with and without the dihydropyridine calcium channel agonist BAY R 5417. Unitary currents decreased on membrane depolarization, with a slope conductance of 19.4 pS (80 mM barium). Channel open-state probability (Po) was steeply voltage dependent. Peak Po during test pulses from -70 mV increased e-fold per 4.5-mV depolarization. Mean peak Po at potentials positive to +10 mV was 0.44. Po at steady membrane potentials was also steeply voltage dependent, changing e-fold per 4.5 mV in the absence of inactivation. Steady-state Po at positive potentials was substantially lower than peak Po elicited by test pulses, suggesting that steady-state inactivation can reduce Po by as much as 10-fold. Membrane depolarization decreased the longest mean closed time but had little effect on the mean open time of single calcium channels measured during steady-state recordings. Lowering the external barium concentration from 80 to 10 mM reduced the single channel conductance to 12.4 pS and shifted the relationship between steady-state Po and membrane potential by about -30 mV. BAY R 5417 also shifted this relationship by about -15 mV.

Ethacizin blockade of calcium channels: a test of the guarded receptor hypothesis

1989 ◽  
Vol 257 (5) ◽  
pp. H1693-H1704
Author(s):  
C. F. Starmer ◽  
A. I. Undrovinas ◽  
F. Scamps ◽  
G. Vassort ◽  
V. V. Nesterenko ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Cell Voltage ◽  
Membrane Potentials ◽  
Specific Rate ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Channel Inactivation ◽  
Ventricular Cells ◽  
Channel Blocking ◽  
Voltage Dependent

The effect on calcium channels of the sodium channel antagonist, ethacizin, was studied in isolated frog ventricular cells using the whole cell voltage-clamp methodology. Ethacizin was found to block inward calcium current in a frequency-, voltage-, and concentration-dependent manner. The frequency-dependent blocking properties were modeled by considering the drug interaction with a voltage-dependent mixture of calcium channels harboring either an accessible or an inaccessible binding site. With repetitive stimulation, the pulse-to-pulse reduction in peak current is shown to be exponential, with a rate linearly related to the interstimulus interval and the drug concentration. Observed frequency- and concentration-dependent blocks were consistent with the predictions of the model, and mixture-specific rate constants were estimated from these data. The negligible shift in channel inactivation and the reduction of apparent binding and unbinding rates with more polarized membrane potentials imply the active moiety of ethacizin blocks open channels and is trapped within the channel at resting membrane potentials. The binding rate at 0 mV is similar to that observed in studies of interactions of other open channel blocking agents with voltage- and ligand-gated channels.

Voltage-dependent calcium channels in ventricular cells of rainbow trout: effect of temperature changes in vitro

2000 ◽  
Vol 278 (6) ◽  
pp. R1524-R1534 ◽  
Author(s):  
Catherine S. Kim ◽  
Mary D. Coyne ◽  
Judith K. Gwathmey
Keyword(s):  
Rainbow Trout ◽  
Calcium Channels ◽  
Temperature Sensitivity ◽  
Calcium Currents ◽  
Temperature Dependency ◽  
Patch Clamp Technique ◽  
Ventricular Cells ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels

Voltage-dependent calcium channels (VDCC) in ventricular myocytes from rainbow trout ( Oncorhynchus mykiss) were investigated in vitro using the perforated patch-clamp technique, which maintains the integrity of the intracellular milieu. First, we characterized the current using barium as the charge carrier and established the doses of various pharmacological agents to use these agents in additional studies. Second, we examined the current at several physiological temperatures to determine temperature dependency. The calcium currents at 10°C (acclimation temperature) were identified as l-type calcium currents based on their kinetic behavior and response to various calcium channel agonists and antagonists. Myocytes were chilled (4°C) and warmed (18 and 22°C), and the response of VDCC to varying temperatures was observed. There was no significant dependency of the current amplitude and kinetics on temperature. Amplitude decreased 25–36% at 4°C (Q10 ∼1.89) and increased 18% at 18°C (Q10 ∼1.23) in control, Bay K8644 (Bay K)-, and forskolin-enhanced currents. The inactivation rates (τi) did not demonstrate a temperature sensitivity for the VDCC (Q10 1.23–1.92); Bay K treatment, however, increased temperature sensitivity of τi between 10 and 18°C (Q10 3.98). The low Q10 values for VDCC are consistent with a minimal temperature sensitivity of trout myocytes between 4 and 22°C. This low-temperature dependency may provide an important role for sarcolemmal calcium channels in adaptation to varying environmental temperatures in trout.

Stereoselectivity of Butylidenephthalide on Voltage-dependent Calcium Channels in Guinea-pig Isolated Ileum

1997 ◽  
Vol 49 (11) ◽  
pp. 1121-1125 ◽  
Author(s):  
WUN-CHANG KO ◽  
JOEN-RONG SHEU ◽  
YI-RONG LEU ◽  
SHU-HUEY TZENG ◽  
CHI-MING CHEN
Keyword(s):  
Guinea Pig ◽  
Calcium Channels ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels
Sign in / Sign up

Export Citation Format

Share Document