ELECTRICAL-RESISTANCE MEASUREMENTS ON CEREBRAL CAPILLARY ENDOTHELIAL-CELLS - A NEW TECHNIQUE TO STUDY SMALL SURFACE-AREAS

We present a new method which allows resistance measurements in selected cell monolayer areas with a size of less than one mm(2). Up to now cell-covered macroscopic filters with areas up to 5 cm(2) have been used giving reliable results only in the absence of inhomogeneities or contaminating cells. The new measuring device is posed on the microscope optic to allow an optical characterization of the measuring area and enables us to scan the cell-covered filter. This method has been applied to determine a reversible modulation of the tightness of intercellular contacts between epithelial or endothelial cells in culture. Tight junction resistance is modulated by Ca2+ and basic amino acids in cultured porcine cerebral microvascular endothelial cells that represent the blood-brain barrier.