Heterogeneous expression of the delayed-rectifier K+ currents iK,r and iK,s in rabbit sinoatrial node cells

• Published in: The Journal of physiology 2001-09, Vol.535 (3), p.703-714
• Main Authors: Lei, M., Honjo, H., Kodama, I., Boyett, M. R.
• Format: Article
• Language: English
• Subjects: Original
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.2001.t01-1-00703.x

The electrical activity of sinoatrial node cells is heterogeneous. To understand the reasons for this, the density of the delayed-rectifier K + current and its two components, i K,r and i K,s , as a function of the size (as measured by cell capacitance) of rabbit sinoatrial node cells was investigated using the whole-cell voltage-clamp technique at 35 °C. i K,r and i K,s were isolated using E-4031 and 293B. Features of the E-4031-sensitive and 293B-insensitive currents corresponded well to those of i K,r , while features of the E-4031-insensitive and 293B-sensitive currents corresponded well to those of i K,s . The densities of the outward current under control conditions and the drug-sensitive and -insensitive currents were significantly ( P < 0.01) correlated with cell capacitance, with current densities being greater in larger cells. The effects of partial blockade of i K,r by 0.1 μ m E-4031 on spontaneous action potentials were greater in smaller cells. It is concluded that there are cell size-dependent differences in the density of the i K,r and i K,s components, and these may be involved in the heterogeneity of the electrical activity of single sinoatrial node cells as well as that of the intact sinoatrial node.