Using FluoZin-3 and fura-2 to monitor acute accumulation of free intracellular Cd in a pancreatic beta cell line.

The understanding of cellular Cd accumulation and toxicity is hampered by a lack of fluorescent indicators selective for intracellular free Cd ([Cd]). In this study, we used depolarized MIN6 mouse pancreatic beta cells as a model for evaluating [Cd] detection with commercially available fluorescent probes, most of which have been traditionally used to visualize [Ca] and [Zn]. We trialed a panel of 12 probes including fura-2, FluoZin-3, Leadmium Green, Rhod-5N, indo-1, Fluo-5N, and others. We found that the [Zn] probe FluoZin-3 and the traditional [Ca] probe fura-2 responded most consistently and robustly to [Cd] accumulation mediated by voltage-gated calcium channels. While selective detection of [Cd] by fura-2 required the omission of Ca from extracellular buffers, FluoZin-3 responded to [Cd] similarly in the presence or absence of extracellular Ca. Furthermore, we showed that FluoZin-3 and fura-2 can be used together for simultaneous monitoring of [Ca] and [Cd] in the same cells. None of the other fluorophores tested were effective [Cd] detectors in this model.