Measurement of whole-cell calcium current in voltage-clamped vascular muscle cells.
The direct measurement of transmembrane calcium current in single vascular muscle cells has been accomplished recently using the whole-cell voltage-clamp technique. The small size of the vascular muscle cell and the proportionately smaller magnitude of its inward calcium current necessitate refined instrumentation, but also make the vascular muscle cell an ideal candidate for whole-cell voltage-clamp recording. Calcium current in vascular muscle cells appears to have some, but not all, characteristics in common with calcium currents similarly isolated in neuronal and cardiac cells, including voltage-dependent activation and steady-state inactivation of calcium current, the presence of two current types, and sensitivity to inorganic and organic calcium channel modulating drugs. Future voltage-clamp analysis of calcium currents in vascular muscle is needed to further our understanding of the control of the calcium channels in physiological and pathophysiological states.