Mechanical properties of cultured human airway smooth muscle cells from 0.05 to 0.4 Hz

We investigated the rheological properties of living human airway smooth mu scle cells in culture and monitored the changes in rheological properties i nduced by exogenous stimuli. We oscillated small magnetic microbeads bound specifically to integrin receptors and computed the storage modulus (G') an d loss modulus (G") from the applied torque and the resulting rotational mo tion of the beads as determined from their remanent magnetic field. Under b aseline conditions, G' increased weakly with frequency, whereas G" was inde pendent of the frequency. The cell was predominantly elastic, with the rati o of G" to G' (defined as eta) being similar to 0.35 at all frequencies. G' and G" increased together after contractile activation and decreased toget her after deactivation, whereas eta remained unaltered in each case. Thus e lastic and dissipative stresses were coupled during changes in contractile activation. G' and G" decreased with disruption of the actin fibers by cyto chalasin D, but eta increased. These results imply that the mechanisms for frictional energy loss and elastic energy storage in the living cell are co upled and reside within the cytoskeleton.