The effects of ultraviolet irradiation on the pigment cells of the PET/Wmr mouse epidermis

Epidermal melanocytes in mammals are known to occur in a variety of shapes, sizes, and colors. The basic melanocyte morphology is dependent upon genetics, but there are a number of environmental factors that can cause modification. In the epidermis of PET/\vrnr mice, the population of rnelanocytes reaches a peak and begins to decline during the first post-natal week, and has disappeared within four weeks. Dispersed among the large, highly DOPA-reactive melanocytes are miniature melanocytes. These miniature melanocytes are weakly DOPA-reactive and appear early in the post-natal period. The miniature melanocyte population is relatively constant and these miniature cells are among the last to disappear. The melanocytes of the. epidermis in the PET/Hmr mouse were subjected to 3 different wavelengths of UV irradiation. Y~lanocyte counts of the experimental animals were compared with similar counts of control, nonirradiated anL~als in the first post-natal week. · The evidence indicates that these weakly DOPA-reactive, miniature melanocytes remai~ in fairly constant numbers ·during the first postnatal week, although UV irradiation did provoke a very clear increase in the numbers of the larger, highly DOPA-reactive melanocytes~ That miniature melanocytes persisted throughout the experimental treatments succest that they may represent a separate form of melanocyte.