“…7 and five separate experiments revealed no significant difference in bFGF mRNA level between steady laminar and turbulent, and be- This result suggests that the magnitude of the shear stress stimulus is a more important determinant of bFGF and PDGF-B mRNA levels than the dynamic characteristics ofthe t= 36 dynes/cm2 shear stress at a given time-average magnitude, at least for the N=240 four conditions employed in this study. These findings suggest o=1 0.70 that the endothelial cell, which may be modeled as a viscoelastic structure (40,41 ), behaves as a sensor to the low frequency (average magnitude) of the shear stress stimulus rather than to its higher frequency components (turbulent or pulsatile There has been mounting evidence to suggest that blood flow, and more specifically the resulting shear stress acting on the vessel wall at the endothelial cell, plays a central role in determining vascular structure ( 1, 5, 6) by a process that is dependent on intact endothelium (6). Recent work has also demonstrated that fluid shear stress changes physiological properties of endothelial cells ( 10-1 2, 15, 42).…”