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Rabbit sino-atrial node cells: isolation and electrophysiological properties
1University Laboratory of Physiology, Oxford.
The Journal of Physiology
|September 1, 1990
Summary
Researchers developed a method to isolate single rabbit sinoatrial node cells, crucial for heart rhythm. These cells exhibit natural shape and spontaneous activity, enabling detailed electrophysiological studies of cardiac pacemaking currents.
Area of Science:
- Cardiology
- Electrophysiology
- Cell Biology
Background:
- The sinoatrial node (SAN) is the heart's primary pacemaker.
- Isolating viable single SAN cells is challenging but essential for understanding cardiac rhythm generation.
- Previous studies often used multicellular preparations, potentially obscuring single-cell properties.
Purpose of the Study:
- To develop and validate a method for isolating calcium-tolerant, single rabbit SAN cells that retain their natural morphology.
- To characterize the electrophysiological properties of these isolated single SAN cells using patch-clamp techniques.
- To investigate the behavior of key ionic currents, including the hyperpolarization-activated current (if) and L-type calcium current, in single SAN cells.
Main Methods:
- Isolation of single rabbit SAN cells using a novel method ensuring calcium tolerance and morphological integrity.
- Whole-cell patch-clamp recording to measure ionic currents and action potentials.
- Haematoxylin-Eosin staining to differentiate single cells from aggregates.
- Assessment of L-type calcium current run-down and TTX-sensitive Na+ current.
Main Results:
- Isolated single SAN cells maintained their natural shape and exhibited spontaneous activity.
- Electrophysiological recordings revealed spontaneous activity and time-dependent currents consistent with multicellular preparations.
- L-type calcium current showed a characteristic run-down after a stable period.
- The hyperpolarization-activated current (if) activation varied, with thresholds near maximum diastolic potential in most active cells.
- MnCl2 increased if, likely by inhibiting Na(+)-Ca2+ exchange and increasing intracellular Ca2+.
Conclusions:
- The developed method successfully yields viable, spontaneously active single rabbit SAN cells with preserved morphology.
- These single cells are suitable for detailed electrophysiological studies, providing insights into cardiac pacemaking mechanisms.
- The findings shed light on the properties of key ionic currents and their regulation in SAN cells.