Electrically induced intracellular Ca2+ transient in single ventricular myocytes: Aa useful parameter for the study of cardiac drugs

1. Fluorescent Ca2+ indicators, such as fura-2/AM and calcium green-1, have become one of the most popular tools for measuring intracellular calcium ( [Ca2+](i)). 2. Electrical stimulation triggers a cascade of events in the cardiac muscl e, which results in a [Ca2+](i) transient and, eventually, contraction. The events that occur in electrically induced cardiac myocytes mimic the norma l physiological events in vivo. 3. The electrically induced [Ca2+](i) transient represents influx of Ca2+ f rom outside and mobilization of Ca2+ from the intracellular store and is di rectly related to contraction. Thus, it is more important to determine the electrically induced [Ca2+](i) transient than [Ca2+](i). The [Ca2+](i) tran sient can be easily measured with the spectrofluorescence method using fura 2/AM as the Ca2+ indicator in a single ventricular myocyte preparation. 4. We made use of the results of studies on carbachol, tetrandrine and card iotoxin to illustrate the usefulness of the electrically induced [Ca2+](i) transient in the study of actions of cardiac drugs.