Wall shear stress (WSS), the frictional force between blood and endothelium, is an important
determinant of vascular function. It is generally assumed that WSS remains constant at a
reference value of 15dyn/cm2. In a study of small rodents, we realized that this assumption
could not be valid. This review presents an overview of recent studies in large and small
animals where shear stress was measured, derived from velocity measurements or
otherwise, in large vessels. The data show that large variations exist within a single species …