Some limitations of the double sucrose gap, and its use in a study of the slow outward current in mammalian ventricular muscle. With an Appendix
Population
Small bundles (diameter 0.8-1.2 mm) of sheep or calf ventricular fibres
Design
Preclinical
Authors
Discussion
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Implication
Animal data on slow outward currents leave open their role in human repolarization; further translational studies required before clinical consideration.
Key Points
- This study aims to explore the limitations of the double sucrose gap method for examining slow outward currents in ventricular muscle fibers.
- Described double sucrose gap method for sheep and calf ventricular fibers (0.8-1.2 mm)
- Measured action potentials using micro-electrode recordings to compare slow and rapid currents
- Derived equations for voltage distribution and leakage current in the double sucrose gap
- Good agreement between micro-electrode recordings and externally recorded potentials
- Slow outward current increases do not significantly contribute to repolarization in sheep or calf
- Accumulation of K ions around cells affects potential distribution during clamps
Structured PICO
P
Population
Small bundles (diameter 0.8-1.2 mm) of sheep or calf ventricular fibres
I
Intervention
Double sucrose gap method (voltage clamp)
O
Outcome
Measurement of slow outward current and action potentialssurrogate
The double sucrose gap method is suitable for studying slow currents in mammalian ventricular muscle, revealing that slow outward current contributes little to repolarization in sheep or calf.
Limitations
- The rapid sodium inward current was not controlled on depolarizing clamp steps
- The method is only suitable for a study of slow currents
- Too small a gap causes membrane current to be swamped by leakage current, while too wide a gap gives unequal potential distribution
Cite This Study
McGuigan et al. (1974) studied this question.