Fluorescence microplate-based techniques for the high-throughput assessment of calcium signaling: The highs and lows for calcium researchers

As discussed throughout this book, the development of calcium-sensitive indicators based on the calcium chelator BAPTA revolutionized the study of cellular calcium homeostasis (Chapter 1). The first two decades of the assessment of cytoplasmic calcium ([Ca]CYT) using calcium-sensitive fluorescence indicators (such as fluo-3 and fura-2) were dominated by studies involving cuvette- and microscope-based equipment. Critically, the choice of this equipment dictates the spatial resolution of the calcium measurements, where large cell populations are used in cuvettes, and microscopes allow single-cell and subcellular measurements. In recent years, exciting methodology has emerged based on fluorescence microplate readers, a development spurred on by the needs of pharmaceutical companies to efficiently screen and identify bioactive molecules and therapeutic agents [1, 2]. As discussed in Chapter 17, the ubiquitous calcium signal has taken a leading role in this respect, with an array of advanced fluorescence microplate readers available that are particularly suited for the high-throughput (HT) assessment of [Ca]CYT