Endothelins (ETs) work as growth factors for fibroblastic growth. Keloids are clinically unpleasant scars within the skin that grow beyond the confines of the original wound. We compared the expression of ET receptors between human skins with hypertrophic scars and keloids, by using our quantitative receptor imaging system. The ET receptor binding sites were distributed in skin areas anatomically corresponding to the epidermis, the superficial and deep dermis, and the vascular bed. The ETA receptor was apparently observed in the skin areas, whereas the ETB receptor was only slightly detected, as deduced from the finding that mRNA encoding the human ETA receptor is expressed in the fibroblast and the vascular bed. The ETA receptor densities of keloid and highly hypertrophic scar were significantly higher than those of normal skin and moderately and mildly hypertrophic scar. There seemed to be no differences in the density between keloid and highly hypertrophic scar. In a keloid skin we noted a possible existence of atypical vascular bed ETA receptor with a low affinity to ETA antagonist of PD151242 and FR139317. The ETA receptor of endogenous growth factors possibly play an etiological role in dysfunctions of the fibroblast in hypertrophic scars, and a typical ETA receptor may be related to the growth of keloid
