Abstract
Attenuated L-type Ca$^2+$ current (I(Ca,L)), or current-contraction
gain have been proposed to explain impaired cardiac contractility
in congestive heart failure (CHF). Six weeks after coronary artery
ligation, which induced CHF, left ventricular myocytes from isoflurane-anesthetized
rats were current or voltage clamped from -70 mV. In both cases,
contraction and contractility were attenuated in CHF cells compared
with cells from sham-operated rats when cells were only minimally
dialyzed using high-resistance microelectrodes. With patch pipettes,
cell dialysis caused attenuation of contractions in sham cells, but
not CHF cells. Stepping from -50 mV, the following variables were
not different between sham and CHF, respectively: peak I(Ca,L) (4.5
+/- 0.3 vs. 3.8 +/- 0.3 pApF(-1) at 23 degrees C and 9.4 +/- 0.5
vs. 8.4 +/- 0.5 pApF(-1) at 37 degrees C), the bell-shaped voltage-contraction
relationship in Cs$^+$ solutions (fractional shortening, 15.2 +/-
1.0\% vs. 14.3 +/- 0.7\%, respectively, at 23 degrees C and 7.5 +/-
0.4\% vs. 6.7 +/- 0.5\% at 37 degrees C) and the sigmoidal voltage-contraction
relationship in K$^+$ solutions. Caffeine-induced Ca$^2+$
release and sarcoplasmic reticulum Ca$^2+$-ATPase-to-phospholamban
ratio were not different. Thus CHF contractions triggered by I(Ca,L)
were normal, and the contractile deficit was only seen in undialyzed
cardiomyocytes stimulated from -70 mV.
- 5-ht4,
- abstract,
- action
- adrenergic
- adrenergic,
- agents,
- alpha-agonists,
- alpha-antagonists,
- amp,
- anesthesia,
- anesthetics,
- animals,
- antibodies,
- antibody
- atpase,
- beta-agonists,
- beta-antagonists,
- binding,
- blotting,
- c57bl,
- caffeine,
- calcium
- calcium,
- calcium-binding
- carbazoles,
- cardiac,
- cardiomegaly,
- cardiotonic
- carrier
- cell
- cells,
- channels,
- comparative
- competitive,
- computer-assisted,
- concentration,
- confocal,
- congestive,
- constriction,
- contraction,
- coronary
- cultured,
- cyclic
- diagnosis,
- differential,
- direct,
- doppler,
- dose-response
- drug,
- echocardiography,
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