The effects of topical nitrogen mustard on the pigment system in PET/Wmr mouse epidermis

Miniature melanocytes have been observed scattered among the typical melanocytes in the skin of the PET/Wmr mouse strain, They are weakly DOPA reactive and their cell bodies and nuclei are one quarter the size of those in typical melanocytes, Both populations reach a peak during the first postnatal week and then gradually disappear within the following three weeks. The miniatures appear very early and are among the last cells to disappear. During the first postnatal week, their population remains relatively constant against a radically changing population of typical melanocytes. That they may represent a stage in the development of typical melanocytes has been the subject of previous experiments using UVL, and heterologous and homologous grafting to stimulate differentiation into typical melanocytes. The present study extends these experiments by employing topical applications of nitrogen mustard to stimulate differentiation. All three studies have failed to alter the relationship between the two melanocyte populations. It is concluded that the miniat~ melanocytes represent a distinct cell type in the epidermis of the PET/Wmr mouse I