Using gadolinium to identify stretch-activated channels: technical considerations

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Abstract
Gadolinium (Gd3+) blocks cation-selective stretch-activated ion channels (SACs) and thereby inhibits a variety of physiological and pathophysiological processes. Gd3+sensitivity has become a simple and widely used method for detecting the involvement of SACs, and, conversely, Gd3+insensitivity has been used to infer that processes are not dependent on SACs. The limitations of this approach are not adequately appreciated, however. Avid binding of Gd3+to anions commonly present in physiological salt solutions and culture media, including phosphate- and bicarbonate-buffered solutions and EGTA in intracellular solutions, often is not taken into account. Failure to detect an effect of Gd3+in such solutions may reflect the vanishingly low concentrations of free Gd3+rather than the lack of a role for SACs. Moreover, certain SACs are insensitive to Gd3+, and Gd3+also blocks other ion channels. Gd3+remains a useful tool for studying SACs, but appropriate care must be taken in experimental design and interpretation to avoid both false negative and false positive conclusions.