Single Isolated Cardiac Myocytes Frozen During Voltage-Clamp Pulses: A Technique for Correlating X-Ray Microanalysis Data on Calcium Distribution with Calcium Inward Current in the Same Cell

1989 ◽  
pp. 265-279
Author(s):  
Maria Fiora Wendt-Gallitelli ◽  
Gerrit Isenberg
Keyword(s):  
Voltage Clamp ◽  
Cardiac Myocytes ◽  
Inward Current ◽  
X Ray ◽  
Calcium Distribution ◽  
Isolated Cardiac Myocytes ◽  
Calcium Inward Current

Effects of acidosis on Na+/Ca2+ exchange and consequences for relaxation in guinea pig cardiac myocytes

1994 ◽  
Vol 267 (2) ◽  
pp. H477-H487 ◽  
Author(s):  
C. M. Terracciano ◽  
K. T. MacLeod
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Intracellular Acidosis ◽  
Rapid Cooling ◽  
Inward Current ◽  
Fluorescence Transient ◽  
Isolated Cardiac Myocytes ◽  
Rate Of Decline ◽  
The Times ◽  
Exchange Activity

We investigated the effect of intracellular acidosis (imposed by NH4Cl prepulses) on the relaxation and decline in intracellular Ca2+ (using indo 1 fluorescence) of isolated cardiac myocytes from the guinea pig. Acidosis produced a decrease in contraction and a prolongation of the fluorescence transient. The rate of decline in fluorescence after a rapid-cooling contracture was slower in acidosis compared with control. The decline in fluorescence after a rapid-cooling contracture in the presence of 10 mM caffeine was greatly slowed during acidosis, suggesting that Na+/Ca2+ exchange is affected. We recorded indo 1 fluorescence and the transient inward current in voltage-clamped cells on rapid application of 10 mM caffeine under control conditions and in acidosis. The amplitude of the transient increase in fluorescence was reduced in acidosis and the decline in fluorescence slowed. The current showed no difference in amplitude in acidosis, but the time to 50% recovery was increased by 57%. When amiloride or ethylisopropylamiloride was present, no differences in the current were found between control and acidosis, and the times to 50% recovery were similar. We conclude that intracellular acidosis slows Ca2+ efflux via Na+/Ca2+ exchange because of an increase in intracellular Na+ due to enhanced Na+/H+ exchange activity.

l-Arginine ameliorates effects of ischemia and reperfusion in isolated cardiac myocytes

2003 ◽  
Vol 476 (1-2) ◽  
pp. 45-54 ◽  
Author(s):  
Adrian Au ◽  
William E. Louch ◽  
Gregory R. Ferrier ◽  
Susan E. Howlett
Keyword(s):  
Cardiac Myocytes ◽  
Ischemia And Reperfusion ◽  
Isolated Cardiac Myocytes

Voltage Sensitive Ca-Channels and the Transient Inward Current in Paramecium Tetraurelia

1979 ◽  
Vol 78 (1) ◽  
pp. 149-161 ◽  
Author(s):  
YOUKO SATOW ◽  
CHING KUNG
Keyword(s):  
Voltage Clamp ◽  
Resting Potential ◽  
Ca Channel ◽  
Paramecium Tetraurelia ◽  
Ca Channels ◽  
Action Current ◽  
Inward Current ◽  
Transient Inward Current ◽  
Inorganic Cation ◽  
Inward Currents

Transient inward currents across the membrane of P. tetraurelia are recorded upon step depolarizations with a voltage clamp in solutions where Ca2+ is the only added inorganic cation. It is shown that the current is normally carried by Ca2+ through the Ca-channels which activate and inactivate in time. The transient inward current is dependent on both the size of the depolarizing step and the holding level before the step. Maximum inward current (Imax) occurs when the membrane is first held at the resting level (- 30 mV), then stepped to 0 mV in a solution containing 0.91 mM-Ca2+. The Imax is smaller when the membrane is first held at depolarized level. This is due to the depolarization-sensitive inactivation of the Ca-channels. The Imax is also smaller when the membrane is first held at a hyperpolarized level. This may be explained by the activation of hyperpolarization-sensitive K-channels known to exist in the Paramecium membrane. I max increases with concentration of Ca2+ up to 0.9 mM. Further increase in the Ca2+ concentration does not affect Imax. This apparent saturation at 0.9 mM-Ca2+ may reflect a rate-limiting step of Ca2+ permeation. The increase in Ca2+ concentration shifts the V-Ipeak curve in the direction of less sensitivity. This result is best explained as the effect of bound Ca2+ on the surface potential of the Paramecium membrane. These results provide the first detailed description of the properties of the action current through the Ca-channel in Paramecium. They also define the conditions under which future voltage-clamp studies of wild-type and mutant membranes of P. tetraurelia should be performed, i.e. to maximize the resolution of the Ca-channel activity, the membrane should be held at or near the resting potential and there should be over 0.9 mM-Ca2+ in the test solutions. The behaviour of the Paramecium Ca-channel and small Imax in the presence of K+ are discussed.

Differential effects of phospholamban and Ca2+/calmodulin-dependent kinase II on [Ca2+]i transients in cardiac myocytes at physiological stimulation frequencies

2008 ◽  
Vol 294 (5) ◽  
pp. H2352-H2362 ◽  
Author(s):  
Andreas A. Werdich ◽  
Eduardo A. Lima ◽  
Igor Dzhura ◽  
Madhu V. Singh ◽  
Jingdong Li ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Sarcoplasmic Reticulum ◽  
Cardiac Myocytes ◽  
Wild Type ◽  
Dependent Protein Kinase ◽  
Frequency Dependent ◽  
Physiological Range ◽  
Dependent Protein ◽  
Isolated Cardiac Myocytes

In cardiac myocytes, the activity of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) is hypothesized to regulate Ca2+ release from and Ca2+ uptake into the sarcoplasmic reticulum via the phosphorylation of the ryanodine receptor 2 and phospholamban (PLN), respectively. We tested the role of CaMKII and PLN on the frequency adaptation of cytosolic Ca2+ concentration ([Ca2+]i) transients in nearly 500 isolated cardiac myocytes from transgenic mice chronically expressing a specific CaMKII inhibitor, interbred into wild-type or PLN null backgrounds under physiologically relevant pacing conditions (frequencies from 0.2 to 10 Hz and at 37°C). When compared with that of mice lacking PLN only, the combined chronic CaMKII inhibition and PLN ablation decreased the maximum Ca2+ release rate by more than 50% at 10 Hz. Although PLN ablation increased the rate of Ca2+ uptake at all frequencies, its combination with CaMKII inhibition did not prevent a frequency-dependent reduction of the amplitude and the duration of the [Ca2+]i transient. High stimulation frequencies in the physiological range diminished the effects of PLN ablation on the decay time constant and on the maximum decay rate of the [Ca2+]i transient, indicating that the PLN-mediated feedback on [Ca2+]i removal is limited by high stimulation frequencies. Taken together, our results suggest that in isolated mouse ventricular cardiac myocytes, the combined chronic CaMKII inhibition and PLN ablation slowed Ca2+ release at physiological frequencies: the frequency-dependent decay of the amplitude and shortening of the [Ca2+]i transient occurs independent of chronic CaMKII inhibition and PLN ablation, and the PLN-mediated regulation of Ca2+ uptake is diminished at higher stimulation frequencies within the physiological range.

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