Simultaneous analysis of intracellular pH and Ca²+ from cell populations

Manipulation of cell function through stable transfection of agonist-specific receptors, components of second messenger cascades, or proteins with specific functional activities (enzymes, transporters, channels) has provided the tools to study intra- and intercellular signaling phenomena at a molecular level. In addition, cotransfection of cells with sequences coding for fluorescent markers such as green fluorescent protein has facilitated the selection and analysis of transfected cells. Techniques are also required to screen for and to monitor the functional changes associated with the genetic manipulation in order to investigate the physiological role of a component within a complex system such as a cell. Hormones and other agonists often elicit changes in intracellular pH (pH(in)) and/or calcium ([Ca(2+)](i)) that modulate cell responses. Thus, methods for comparing steady-state ion concentrations and the regulation of these ions between cell populations in which signaling pathways have been modified can provide an approach to screen for functional changes in signal transduction for selective agonists.