Autoradiographic detection of substance P receptors in normal and psoriatic skin.

Substance P has been detected in human skin and has been implicated in the pathogenesis of certain inflammatory cutaneous disorders. However, little is known about the number and distribution of substance P binding sites in the skin. Receptor autoradiography was employed to detect and quantitate substance P receptors in normal as well as psoriatic skin. Substance P binding sites were distributed in the epidermis and dermis both in normal and psoriatic skin. In the dermis, the highest densities of SP binding sites were found in the areas corresponding to the dermal papillae and the adnexal structures. Quantitative analysis revealed that saturable binding was obtained both in the epidermis and in the labeled dermal areas. Rosenthal plot values were consistent with a single population of binding sites. No difference in the binding measurements was observed between normal and psoriatic skin. The presence of substance P receptors in the epidermis and in the dermal papillae raises interesting issues on the possible targets of this peptide in human skin both under physiologic and pathologic conditions.