A Systematic Approach for Assessing Ca²⁺ Handling in Cardiac Myocytes

Abstract

In cardiac myocytes, Ca²⁺ release from the sarcoplasmic reticulum (SR) Ca²⁺ store through the opening of ryanodine receptors (RyRs) is the major source of Ca²⁺ for activation of myofilaments and contraction. Over the past 20 years, tools have become available to study this release process in detail, allowing new insights into the regulation of SR Ca²⁺ release and RyR function. To assess these processes, we recommend and here review a systematic approach that evaluates the essential transport mechanisms and Ca²⁺ fluxes in isolated single cardiac myocytes by using fluorescent Ca²⁺ indicators and whole-cell recording of membrane voltage and ionic currents under voltage clamp. The approach includes an assessment of the L-type Ca²⁺ current as a trigger for opening of RyRs and release of SR Ca²⁺, of the SR Ca²⁺ content, of intrinsic properties of RyRs, and of Ca²⁺-removal systems.