Measurement of intracellular calcium ion activity with neutral exchanger ion sensitive microelectrodes

Micropipettes filled with the neutral liquid ion exchanger ETH 1001 can be used to make microelectrodes that are sensitive to cytoplasmic levels of Ca2+. They are high resistance electrodes, so that care is required in order to record the low current signal. The electrodes often yield 10-15 mV change between intracellular Ca2+ activities of 10(-6) and 10(-7) M, according to a log relation. The microelectrodes are non-destructive, even in rather small cells, and can be used to monitor Ca2+ changes during experimental interventions.