Use of electrochemical impedance measurements to monitor beta-adrenergic stimulation of bovine aortic endothelial cells

Due to the high permeability of endothelial cell layers derived from macrov ascular vessels, precise determination of their barrier function towards io n movement requires refined experimental techniques. We thus cultured bovin e aortic endothelial cells (BAEC) directly on thin gold-film electrodes and measured the electrochemical impedance to study their passive electrical p roperties in general and during beta-adrenergic stimulation. Impedance spec tra (10(-2).10(6) Hz) of confluent cell monolayers revealed that the electr ical characteristics of the cells can be modelled by a simple resistor-capa citor parallel network. Under control conditions the overall resistance of confluent BAEC monolayers was 3.6+/-0.6 Ohm.cm(2) (n=30) and the capacitanc e was 0.6+/-0.1 mu F/cm(2). Both quantities are discussed with respect to m orphological characteristics of these cells. Stimulation of BAECs with the synthetic beta-adrenoceptor agonist isoproterenol leads to a concentration- dependent, highly specific increase of the cell layer resistance characteri zed by a concentration for half-maximal response (EC50) of 0.3+/-0.1 mu M. The cell layer capacitance, however, remained unaffected. Using impedance m easurements at a single frequency, we analysed the response of BAECs to tre atment with isoproterenol in comparison with several chemically unrelated c ompounds known to stimulate the adenosine 3',5'-cyclic monophosphate (cAMP) -dependent signal transduction cascade. These studies confirmed that the en hancement of the cell layer resistance after beta-adrenergic stimulation is mediated by an increase in intracellular cAMP.