Does anyone have any advice or experience with loading cells (esp cardiac myocytes) with sodium green for sodium measurements. I have tried various loading procedures (with and without pluronic, diff concentrations and temperatures) but only get a very faint signal in resting myocytes. When exposed to conditions that should cause a rise in intracellular sodium (gramicidin, hypoxia, ouabain) there is no change in fluorescence. The fluorophore is being excited with the 488 line on a MRC600 and imaged at around 530nm. Any ideas ? Ian.