Functional Microvascular Dysfunction: Endothelial and Smooth Muscle Abnormalities.

Coronary blood flow is regulated by oxygen demand through coordinated control of vascular resistance within different domains. Endothelial cells represent an important key factor in the regulation of coronary microvascular tone throughout synthesis and releasing of different vasodilator substances. The main vasodilator factor, produced by the endothelial cells, is nitric oxide. Endothelin-1 is a potent vasoconstrictor peptide which stimulates the proliferation of smooth muscle cells. Vessels smooth muscle cells play a major role in the pathogenesis of endothelium-independent coronary regulation of the vascular tone, principally mediated by Rho-kinase activation.