In recent years, the cutaneous microcirculation has gained increasing interest as it represents an easily accessible and potentially representative vascular bed to examine the mechanisms of microcirculatory function and dysfunction. Apart from maintaining nutrition to the skin tissues, it is decisively engaged in thermoregulation. Although the quantitative measurement of skin blood flow (SkBF) remains a problem, rough estimates of SkBF range between 200 to 500 ml/l at rest and may attain up to 7-8 l/min during maximal vasodilatation. It is obvious that the regulation of SkBF is a complicated phenomenon; SkBF is regulated by a complex interplay of centrally mediated neural mechanisms as well as by local humoral and metabolic factors.

The endothelium plays a crucial role by releasing a number of vasodilators and vasoconstrictors in response to different physical (shear stress, pulsatility) and pharmacological stimuli. The most investigated vasodilators are nitric oxide, prostaglandins and endothelium-derived hyperpolarizing factor. In spite of several investigations, the exact interplay of these mechanisms is still not well defined, specially not in human skin microcirculation. The phenomenon is more complicated by the fact that the contribution of each of these mediators to the endothelium-dependent vasodilatation varies depending on the measuring site (glabrous vs. nonglabrous area) as well as on the agonist used to stimulate the endothelium. Elucidating the role of endothelial vasodilators in human skin microcirculation is important also from the clinical point of view as early detectable endothelial dysfunction might precede clinical manifestation of the disease states. On the other hand, it has been shown that endurance training leads to an enhancement of endothelium-dependent vasodilatation in human microcirculation.

Using laser Doppler flowmetry, cutaneous microvascular responses to physiological and pharmacological stimuli are currently being investigated as indices of vascular function. The stimuli mostly used include postocclusive reactive hyperemia, whole body heating and/or cooling, local heating/cooling, and the application of specific pharmacologic agents by iontophoresis, intradermal microdialysis or microinjection. The unpleasant limitation of studying human skin microcirculation is the demand of noninvasiveness. The overview will present some new insights in the physiology and pharmacology of skin microcirculation with emphasis on endothelial function as well as potentially beneficial adaptations of skin micorcirculation to exercise.