A computer-based system for the measurement of membrane capacitance to monitor exocytosis in secretory cells.

A software-based system for real-time measurement of membrane capacitance was developed for monitoring exocytosis in a single cell. The IBM PC compatible software, linked to an interface box, provides capacitance measurement capabilities to a patch-clamp setup utilizing a Labmaster data acquisition board. In order to measure the time-dependent changes in membrane capacitance, the system uses a software-based phase detector which isolates capacitive membrane current from a cell subject to sinusoidal voltage stimulation. The sampling program can monitor changes in membrane capacitance in response to depolarizing voltage steps, intracellular calcium stimulation, or drug application. A separate analysis program was constructed to implement the quantitative analysis, plotting and exporting of the capacitance, conductance and current data acquired by the sampling program.