The immediate action of long-wave ultraviolet radiation (UVA) on suprabasal melanocytes in human skin: a transmission electron microscopical study.

The immediate effects of long-wave ultraviolet irradiation (UVA) in non-erythemal doses on suprabasal melanocytes in normal skin of healthy caucasians with skin types II and III was investigated with the transmission electron microscopy (TEM) in order to detect possible morphological changes. In skin type III the melanocytes remained essentially unaltered, but in skin type II, multiple pinocytotic vesicles, large vacuoles, swelling, and partial to total dissolution of the inner membranes of the mitochondria and numerous small vesicles associated with an enlarged Golgi apparatus were observed after 3.6 to 14.5 J/cm2 of UVA irradiation. No IPD reaction was observed in any of the subjects with skin type II irradiated with UVA up to 20 J/cm2.