[Clinical significance of endothelial dysfunction: studies of human coronary circulation in vivo].

One of the most fascinating findings concerning our knowledge on the physiology of the cardiovascular system, especially the coronary circulation, concerns the modulating capacity of the endothelial cells on the tone of smooth muscle cells. This phenomenon was described for the first time in the aorta of a rabbit in 1980 by Furchgott and Zawadzki using acetylcholine as stimulator. Later, however, it became clear that other substances that are likewise of interest in the context of coronary heart disease, like thrombin, serotonin and histamine, have the same effect on endothelial cells. These effects can also be demonstrated in the human coronary circulation during cardiac catheterization. While normal coronary segments show a vasodilatation (corresponding to the endothelial relaxation in vitro) in arteriosclerotic coronary segments, vasoconstriction is induced by acetylcholine and serotonin. A disturbance of this vasomotor process mediated by endothelial vasomotor processes may be of particular importance in instable angina pectoris and for the development of myocardial infarction.