Characterizing the Trigger for Sarcoplasmic Reticulum Ca²⁺ Release in Cardiac Myocytes

Abstract

Here, we describe a method for characterizing the L-type Ca²⁺ current, I_CaL, which is a major trigger for Ca²⁺ release from the sarcoplasmic reticulum (SR). The protocol includes measuring I_CaL amplitude and voltage dependence and the elicited SR Ca²⁺ release. The procedure for measuring I_CaL activity is performed using solutions (internal and external) and voltage control such that other ionic currents are eliminated. The resultant relationship between the Ca²⁺ current and the associated internal [Ca²⁺]_i transient is a first approach for evaluating coupling gain. We discuss which parameters are most appropriate for this analysis and how an evaluation of gain needs to be further explored by measuring the SR Ca²⁺ content.