Fig.8 is an example in which the cytosolic free Ca2+ fluctuations were recorded simultaneously with the contractile activity of the neonatal cardiomyocytes. In this experiment lysophophatidylcholine (LPC), an amphiphile, was the toxic agent. It has been incriminated as one of the endogenous chemical mediators of ventricular arrhythmias in ischemic myocardium, which accumulates very early in the ischemic heart. In Fig 8A are shown the simultaneous tracings of myocyte contraction (top) and cytosolic free Ca2+ levels as estimated by 360/380 nm fluorescence intensity ratio of Fura 2 (lower tracing) in a spontaneously contracting control myocyte before and after the addition of EPA (10 μM) to the superfusate.