[Endothelins--properties, formation, mechanism of action and significance]

In endothelial cells of the blood vessels and in other cell types by the cleavage of precursor-molecules 21 amino acids containing peptides--the endothelins--are formed. There exist 3 isoforms. The synthesis of endothelin 1 in the endothelial cells is stimulated by adrenaline, noradrenaline, angiotensin II, arginine-vasopressin, thrombine, interleukin 1 and hypoxia. Receptors for endothelins are distributed in most tissues. A significance of the endothelins apparently exists in the stimulation of the activity of the heart and in the vasoconstriction in the case of a decrease of the blood pressure (when blood is lost) and of hypoxia. Endothelins are also formed in the lungs, the kidneys, the brain and the eye. In experimental animals already a low dose of endothelin has a lethal effect by inducing disturbances in the cardiovascular system. By the snake species Atractaspis engaddensis formed sarafotoxins have a similar structure as the endothelins and are effective by binding to their receptors.