CORTICOTROPIN EXPRESSION BY HUMAN MELANOCYTES IN THE SKIN

Highly dendritic melanocytes have been observed in rapidly proliferati ng seborrheic keratosis, epidermis overlying melanomas, and in melanom as. On staining for the presence of POMC with monoclonal antibody agai nst human ACTH, the melanocytes show cytoplasmic positivity. Short ter m organ cultures of whole skin from the marginal zone of vitiligo pati ents show that 22.7% of controls and 45.5% on dark incubation in adria mycin and 87.5% exposed to a pulse of UV on adriamycin treatment show melanocytes positive for ACTH. The surrounding keratinocytes in the ep idermis and in the seborrheic keratosis are negative, whereas in melan omas, isolated groups of melanocytes are positive for ACTH. These find ings indicate that ACTH is expressed by the melanocytes in the G(2)-ph ase, the activity being enhanced on UV exposure. Thus UV dependent pig mentation is associated with POMC production in human skin. From this work it is evident that the melanocyte network varies the MSH/ACTH lev els in correlation with repigmentation and depigmentation in the margi nal zone in vitiligo by expressing POMC locally and is related to the W-sensitivity of the melanocytes.