AJP - Cell Physiology, Vol 259, Issue 3 C375-C388, Copyright © 1990 by American Physiological Society
Development and biological applications of chloride-sensitive fluorescent indicators
A. S. Verkman
Department of Medicine, University of California, San Francisco 94143.
Chloride movement across cell plasma and internal membranes, is of central
importance for regulation of cell volume and pH, vectorial salt movement in
epithelia, and, probably, intracellular traffic. Quinolinium-based
chloride-sensitive fluorescent indicators provide a new approach to study
chloride transport mechanisms and regulation that is complementary to 36Cl
tracer methods, intracellular microelectrodes, and patch clamp. Indicator
fluorescence is quenched by chloride by a collisional mechanism with
Stern-Volmer constants of up to 220 M-1. Fluorescence is quenched
selectively by chloride in physiological systems and responds to changes in
chloride concentration in under 1 ms. The indicators are nontoxic and can
be loaded into living cells for continuous measurement of intracellular
chloride concentration by single-cell fluorescence microscopy. In this
review, the structure-activity relationships for chloride-sensitive
fluorescent indicators are described. Methodology for measurement of
chloride transport in isolated vesicle and liposome systems and in intact
cells is evaluated critically by use of examples from epithelial cell
physiology. Future directions for synthesis of tailored chloride-sensitive
indicators and new applications of indicators for studies of transport
regulation and intracellular ion gradients are proposed.
