| ECIS
has also been applied to follow the response of confluent bovine aortic
endothelial cells upon stimulation of b-adrenergic receptors with isoproterenol
(ISO), which is a synthetic analogue to adrenaline. The figure on the left
shows the impedance measured at a frequency of 10 kHz as a function of
time while exposing the cells to ISO (arrow). Application of the drug increases
the impedance to a maximum within 10 min and which then slowly declines
(red). Under control conditions no such response could be observed (black).
The impedance increase is due to a ISO-induced relaxation of the cells
and a concomittant decrease of the width of the intercellular cleft.
The
figure on the right shows a dose-response relationship generated from similar
ECIS experiments when the cells were expsoed to varying concentrations
of ISO. The EC50 value
of 0.3 mM is very close to the binding constant of ISO to b-adrenoceptors.
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