A system for producing and monitoring in vitro calcium pulses similar to those observed in vivo.

We have used a computer-controlled automatic pipettor system in conjunction with a fluorescence spectrometer to produce Ca2+ pulses and pulse sequences within a cylindrical fluorescence cuvette. These pulses or pulse sequences are similar to those observed in the cytosol of many types of cells in vivo and show good reproducibility. Their intensity, duration, shape, and periodicity can be controlled and determined at will. Pulses of other ions or of transmembrane potential can be produced by the same apparatus. As an example of the use of this apparatus, initial studies on uptake of pulses of Ca2+ by isolated liver mitochondria are described in which controls are used to verify that initial rapid mitochondrial Ca2+ uptake is actual net uptake, as opposed to binding or exchange.