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.