Presence of immunoreactive beta-endorphin in human skin

The production and its induction by ultraviolet radiation (UVR) of proopiom elanocortin (POMC)-derived peptides by keratinocytes has been reported, alb eit not consistently. Recently we demonstrated that only under specific cul turing conditions human keratinocytes are capable of producing a beta -endo rphin (betaE)-like peptide with the characteristics of beta -lipotropin (be ta LPH). Here the presence and UV-induction of betaE-immunoreactivity (beta E-IR) in keratinocytes in human skin in vivo was investigated. betaE-IR was detectable by immunohistochemistry in keratinocytes of the follicular matr ix and to some extent in cells of sweat ducts, but was absent from epiderma l keratinocytes. Absence of betaE-IR was confirmed by radioimmunoassay of H PLC-fractionated extracts of normal epidermis. Repeated exposure to solar-s imulated UVR had no effect. This investigation is the first to demonstrate the presence of betaE-immunoreactive material in the follicular matrix of c orporal hairs and in duct cells of sweat glands. The possible meaning of th ese results is discussed.