A novel tensile tester has been developed to measure tensile properties of single isolated cells. Both ends of the cell were aspirated with glass micropipettes coated with a cellular adhesive. One pipette was moved with an electrical manipulator to stretch the cell horizontally. The force applied to the cell was measured by the deflection of a cantilever part of the other pipette. The cell was observed with water immersion objectives under an upright microscope to obtain its clear image. Cultured bovine aortic smooth muscle cells were stretched at various strain rate in a physiological salt solution at 37°C. Elastic modulus of the cells had a significant positive correlation with the strain rate, and was about 3 kPa at the strain rate <4%/s. Viscoelastic analysis with a standard viscoelastic solid showed that relaxation time for constant strain of the cells was 164s, which is much longer than those reported for endothelial cells and fibroblasts (40s). Smooth muscle cells may be most viscous among the cells in the vascular wall.
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