Cholinesterase Activity of Human Skin

IT has been suggested that derangements of acetylcholine metabolism in skin may underlie the changes occurring in certain dermatoses. In view of this, more knowledge is needed both of the reactions of skin to acetyloholine and of the enzyme systems concerned in its metabolism in this tissue. The presence of cholinesterase in skin was first demonstrated conclusively by Thompson and Whittaker (1944) and by Zeller, Kocher and Maritz (1944). The former authors, working chiefly with the rat, included two assays on human skin. Ord and Thompson (1950) next showed that activity in rat skin is mainly due to a " non-specific " or pseudo-choHnesterase. Hellmann (1952), using a histochemical technique, reported cholinesterase activity in the sweat glands ofthe pads ofthe cat's paw, also chiefly ofthe " non-specific " type; after sympathectomy this activity disappeared. In skin biopsies of the human axilla, however. Hurley, Shelley and Koelle (1953), also using a histochemical method, found only specific or •' true " cholinesterase ; this was located in the nerve endings to the eccrine sweat glands. They could not detect either type of oholinesterase in other structures in the skin except to a small extent in the blood vessels. In view of these different findings in different species it was decided to undertake a more detailed survey of these enzymes in normal human skin. Because of the limitations of histochemical procedures, we have assayed enzyme activity manometrically using acetyl-^^-methylcholine and butyrylchoUne as substrates for true and pseudo-cholinesterase respectively. We have also used acetylchoUne as substrate, which is hydrolysed by both types of esterase. A few