Hemodynamics and Endothelial Cell Phenotypes in vivo

Introduction Responses of endothelial cells to circulating substances (hormones, growth factors, drugs, agonists, toxic reagents etc) are a function of the particular phenotype of a particular cell(s) at a particular period of time. The endothelial phenotype is determined by 2 distinct components – (i) an intrinsic phenotype imprinted genetically during development that defines the essential identity of the cell, and (ii) elements of the local environment that overlay, modify or enhance characteristics of the intrinsic phenotype. The latter is responsible for much of the ‘plasticity’ of endothelial (and vascular wall) structure and function. Endothelia within different vascular beds express specialized morphologies and functions appropriate to their location. It follows therefore that the scale at which site-specificity of phenotype can be studied ranges from comparisons of entire vascular beds to individual cells at adjacent locations within the same vessel.