3 - Measurement of Whole-Cell Calcium Current in Cardiac Myocytes

Abstract

Publisher Summary This chapter discusses the measurement of whole-cell calcium current in cardiac myocytes. The whole-cell patch-clamp method provides a very powerful means of studying the biophysical properties of surface membrane ionic channels in cardiac cells. It provides direct access to the interior of the cells, thereby, allowing some degree of control of the intracellular metabolic and ionic environment. Unlike the suction pipet method, the pipet used in the patch-clamp method has a smaller tip diameter resulting in larger series resistance and the content of the pipet cannot be exchanged during the course of whole-cell recording. The smaller pipet limits the size of current that can be clamped adequately and the ease of passive diffusion of large molecules into the interior of the cells. Moreover, the whole-cell voltage patch-clamp technique is easier to master because the smaller pipet and the lack of continuous internal perfusion allow easy high-resistance seal formation and maintenance. Unlike the large and fast sodium current, the calcium current can be studied accurately with this method as long as the spatial control of the voltage-clamp system is documented, and currents other than calcium currents are eliminated with appropriate external and internal solutions and holding potential.