Measuring Cardiomyocyte Contractility and Calcium Handling In Vitro.

In vitro measurements of cardiomyocyte contractility and Ca2+ handling have been used as a platform for
determining physiological consequence of various genetic manipulations and identifying potential therapeutic
targets for the treatment of heart failure. The Myocyte Calcium and Contractility System (IonOptix)
offers a simultaneous trace of sarcomere movements and changes of intracellular Ca2+ levels in a single
cardiomyocyte. Herein, we describe a modified protocol for the isolation of adult cardiomyocytes from
murine hearts and provide a step-by-step description on how to analyze cardiomyocyte Ca2+ transient and
contractility data collected using the IonOptix system. In our modified protocol, we recommend a novel
cannulation technique which simplifies this difficult method and leads to improved viability of isolated
cardiomyocytes. In addition, a comprehensive analysis of intracellular Ca2+ handling, SR Ca2+ load,
myofilament Ca2+ sensitivity, and cardiomyocyte contractility is described in order to provide important
insights into myocardial mechanics.