A METHOD FOR RECORDING INTRACELLULAR [CA2-2(] TRANSIENTS IN CARDIAC MYOCYTES USING CALCIUM GREEN)

Calcium green-2 (Ca green) is a non-ratio-metric fluorescent Ca2+ indi cator with an affinity for Ca2+ (dissociation constant K-d = 3 mu M) t hat is lower than more commonly used indicators such as fura-2 and flu o-3. This low Ca2+ affinity, coupled with a high quantum yield, allows cells to be loaded with low concentrations of Ca green, avoiding prob lems of cytosolic Ca2+ buffering and a low signal-to-noise ratio. This communication presents a method for monitoring intracellular [Ca2+] c hanges in isolated rat ventricular myocytes loaded with Ca green and t he fluorescent pH indicator carboxy SNARF-1 (SNARF). SNARF provides a Ca2+-insensitive signal with which Ca green fluorescence can be correc ted for cell motion and dye-loading artifacts.