Vascular function

The vasculature is a dynamic system that is continually undergoing change by adapting to mechanical, hemodynamic, and humoral changes. Central to these processes are vascular smooth muscle cells (VSMC) that constitute the bulk of the vascular media. VSMCs are regulated by many factors that promote contraction, dilation, growth, fibrosis, calcification, and inflammation, which impact on vascular functional and structural changes. Acute regulation of vascular diameter involves activation/deactivation of the contractile machinery, triggered primarily by an increase in intracellular free calcium concentration. Vasoactive agents, such as Ang II, ET-1, bradykinin, and neurotransmitters, regulate vascular function and in pathological conditions contribute to vascular dysfunction and vascular remodeling. Emerging evidence indicates an important role for reactive oxygen species in the regulation of vascular function. Moreover, factors secreted by adipocytes (adipokines) may directly impact on vascular contraction, dilation, growth, and inflammation. Molecular processes underlying these events are complex and involve small G proteins, phospholipases, protein kinase C, mitogen-activated protein kinases, tyrosine kinases, and RhoA-Rho kinase, among others. This chapter addresses mechanisms regulating vascular function (contraction/dilation) and highlights some processes contributing to vascular structural changes (remodeling). Some important vasoactive agents are described, and implications in vascular dysfunction and cardiovascular disease are discussed.