Effects of goniopora toxin on the action potential and membrane currents of guinea-pig single ventricular cells

1988 ◽  
Vol 337 (4) ◽  
Author(s):  
Matomo Nishio ◽  
Ikunobu Muramatsu ◽  
Shigeru Kigoshi ◽  
Motohatsu Fujiwara
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Membrane Currents ◽  
Ventricular Cells ◽  
Goniopora Toxin

Effects of estrogen on action potential and membrane currents in guinea pig ventricular myocytes

1999 ◽  
Vol 277 (2) ◽  
pp. H826-H833 ◽  
Author(s):  
Seiko Tanabe ◽  
Toshio Hata ◽  
Masayasu Hiraoka
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Voltage Dependence ◽  
Ventricular Myocytes ◽  
Membrane Currents ◽  
Patch Clamp Technique ◽  
17Β Estradiol ◽  
Electrophysiological Effects ◽  
Ionic Basis

To explore a possible ionic basis for the prolonged Q-T interval in women compared with that in men, we investigated the electrophysiological effects of estrogen in isolated guinea pig ventricular myocytes. Action potentials and membrane currents were recorded using the whole cell configuration of the patch-clamp technique. Application of 17β-estradiol (10–30 μM) significantly prolonged the action potential duration (APD) at 20% (APD20) and 90% repolarization (APD90) at stimulation rates of 0.1–2.0 Hz. In the presence of 30 μM 17β-estradiol, APD20 and APD90 at 0.1 Hz were prolonged by 46.2 ± 17.1 and 63.4 ± 11.7% of the control ( n = 5), respectively. In the presence of 30 μM 17β-estradiol the peak inward Ca2+ current ( I CaL) was decreased to 80.1 ± 2.5% of the control ( n = 4) without a shift in its voltage dependence. Application of 30 μM 17β-estradiol decreased the rapidly activating component of the delayed outward K+ current ( I Kr) to 63.4 ± 8% and the slowly activating component ( I Ks) to 65.8 ± 8.7% with respect to the control; the inward rectifier K+ current was barely affected. The results suggest that 17β-estradiol prolonged APD mainly by inhibiting the I Kcomponents I Krand I Ks.

Changes in cytosolic calcium monitored by inward currents during action potentials in guinea-pig ventricular cells

1989 ◽  
Vol 238 (1291) ◽  
pp. 171-188 ◽  
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Voltage Clamp ◽  
Action Potentials ◽  
Single Cells ◽  
Calcium Transient ◽  
Cytosolic Calcium ◽  
Time To Peak ◽  
Ventricular Cells ◽  
In Cells

Action potentials were recorded from single cells isolated from guinea-pig ventricular muscle. Contraction was measured with an optical technique. Tail currents thought to be activated by cytosolic calcium were recorded when action potentials were interrupted by application of a voltage-clamp. A family of tail currents was recorded by interrupting the action potential at various times after the upstroke. The envelope of tail current amplitudes was taken as an index of changes in cytosoli calcium. Con­sistent with this interpretation, tail currents were negligible following intracellular loading with the calcium chelator BAPTA to suppress calcium transients. The cytosolic calcium transient estimated from the envelope of tails reached a peak approximately 50 ms after the upstroke of the action potential, and fell close to diastolic levels before repolarization was com­plete; 10 mM caffeine delayed the time to peak contraction, and caused a prolongation of the cytosolic calcium transient estimated from the envelope of tail currents. Caffeine also induced the appearance of a distinct late plateau phase of the action potential. Intracellular BAPTA suppressed the late plateau, contraction and tail currents in cells exposed to caffeine. Exposure to caffeine increased the time constant for decay of tail currents (from approximately 35 to 70 ms). When action potentials were greatly abbreviated by interruption with a voltage-clamp, a pro­gressive decline occurred in the subsequent three contractions and tail currents. There was a progressive reversal of these effects over four responses when the full action potential duration was restored. None of these effects was observed in cells exposed to caffeine. Calcium-activated tail currents appear to be a useful qualitative index of changes in cytosolic calcium. The observations are consistent with the suggestion that cytosolic calcium is reduced during the plateau by a combination of calcium extrusion through Na–Ca exchange and calcium uptake into caffeine-sensitive stores. It also appears that reduction of stores loading during abbreviated action potentials reduces subsequent contraction in cells not exposed to caffeine.

scholarly journals Sodium-calcium exchange during the action potential in guinea-pig ventricular cells.

1989 ◽  
Vol 411 (1) ◽  
pp. 639-661 ◽  
Author(s):  
T M Egan ◽  
D Noble ◽  
S J Noble ◽  
T Powell ◽  
A J Spindler ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Sodium Calcium ◽  
Ventricular Cells ◽  
Calcium Exchange ◽  
Sodium Calcium Exchange

scholarly journals Effects of a novel cardioprotective drug JTV-519 on membrane currents of single ventricular cells of the guinea pig heart

1998 ◽  
Vol 76 ◽  
pp. 285
Author(s):  
Junko Kimura ◽  
Masanori Kawahara ◽  
Eiichi Sakai ◽  
Junichi Yatabe ◽  
Hironori Nakanishi
Keyword(s):  
Guinea Pig ◽  
Membrane Currents ◽  
Guinea Pig Heart ◽  
Ventricular Cells ◽  
Cardioprotective Drug
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