Store-operated calcium channels: how do we measure them, and why do we care?

A major mechanism whereby calcium entry into cells is regulated is the store-operated or capacitative calcium entry pathway. In this article, two basic issues are discussed: (i) the methods investigators use to measure store-operated entry, and (ii) the role played by the store-operated pathway in responses to hormones and neurotransmitters under physiological conditions. The two topics are considered together because they are closely interrelated; as we begin to ask questions about calcium movements at low concentrations of agonists, the technology to measure these movements becomes increasing challenging.