Melanogenesis: Ultrastructural Histochemical Observations on Ultraviolet Irradiated Human Melanocytes

Ultrastructural DOPA and tyrosine reactions have been used to provide information regarding subcellular sites of melanogenesis within the melanocyte following ultraviolet irradiation of normal human skin. Our observations indicate that the earliest premelanosomes arise from all parts of the Golgi apparatus as well as from a Golgi associated system of smooth endoplasmic reticulum (GERL). The time interval following irradiation influences the site of enzyme activity. The role of the Golgi apparatus in melanogenesis is discussed and special attention is drawn to the fact that some premelanosomes frequently show no tyrosinase activity, even though such enzyme activity may be present in neighboring vesicles