Epidermal Lysosomes and Ultraviolet Light

Abstract

Secondary lysosomes of guinea-pig keratinocytes were labeled, in vivo, with an electron microscopic marker (Thorotrast) that can he identified both within stable lysosomes and, after lysosome lysis, in extralysosomal locations. Immediately after irradiation with 10 and 20 minimal erythemal doses delivered from an ultraviolet light source in vivo, the large majority of epidermal lysosomes was intact but occasional lysosomes exhibited ruptured membranes and a spilling at tracer into the cytoplasm. Morphologic signs of early UV damage to the cytoplasm were present immediately alter irradiation but these occurred also in the absence of lysosome Lysis. Unirradiated controls showed no cytoplasmic damage but the same amount of lysosome lysis as the irradiated animals. With regard to lysosomes and lysosome lysis there was no difference between nonirradiated and irradiated animals biopsied immediately after UV-exposure. Two, 6, and 12 hr after irradiation the irradiated animals exhibited a greater degree of lysosome lysis than the controls. It is concluded that lysosome lysis accompanies the UV reaction of the epidermis but the present study provides no evidence that it represents an initial pathogenic event.