June 1, 1994Cardiovascular Research
Phentolamine blocks ATP sensitive potassium channels in cardiac ventricular cells
Key result
Phentolamine (5 microM) reduced KATP channel open probability by 94% in inside-out patches of isolated rabbit ventricular cells, independent of alpha adrenoceptor blockade.
Why the study?
Does phentolamine block ATP-sensitive potassium channels in isolated rabbit ventricular cells?
Population
Isolated rabbit ventricular cells (inside-out and outside-out patches)
Comparison
Phentolamine (5 microM and 50 microM) vs Baseline channel activity
Design
Preclinical
Authors
Discussion
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Implication
Phentolamine may exert ischemia-related antiarrhythmic effects partly via KATP blockade; leaves open translation to human myocardium or clinical arrhythmias.
Key Points
- To determine whether the antiarrhythmic agent phentolamine directly inhibits ATP-sensitive potassium (KATP) channels in cardiac ventricular cells.
- Conducted single-channel patch-clamp recordings on isolated rabbit ventricular cells using inside-out and outside-out membrane patches at room temperature.
- Tested the effects of intracellular and extracellular phentolamine application at concentrations of 5 µM and 50 µM on KATP channel activity.
- Intracellular application of 5 µM phentolamine reduced KATP channel activity in 22 of 26 inside-out patches, decreasing channel open probability by 94% (n=12), with reversible effects in 17 patches.
- A higher concentration of 50 µM phentolamine completely abolished channel activity in 6 of 8 patches, while extracellular 5 µM phentolamine inhibited channel activity in 50% of outside-out patches, lowering open probability by 98% to 100%.
Structured PICO
Does phentolamine block ATP-sensitive potassium channels in isolated rabbit ventricular cells?
P
Population
In vitro single channel experiments performed on inside-out and outside-out patches of isolated rabbit ventricular cells.
I
Intervention
Phentolamine (5 microM and 50 microM)
C
Comparator
Baseline channel activity
O
Outcome
ATP-sensitive potassium channel (KATP) activity (open probability)surrogate
Phentolamine blocks ATP-sensitive potassium channels in cardiac ventricular cells, suggesting its antiarrhythmic effects during ischemia may be partly independent of alpha adrenoceptor antagonism.
Cite This Study
Wilde et al. (1994) studied Isolated rabbit ventricular cells. Phentolamine was evaluated on KATP channel activity (open probability). Phentolamine (5 microM) reduced KATP channel open probability by 94% in inside-out patches of isolated rabbit ventricular cells, independent of alpha adrenoceptor blockade.