MITOCHONDRIAL INCLUSIONS IN KERATINOCYTES OF HAIRLESS MOUSE SKIN EXPOSED TO UVB RADIATION

Mitochondrial inclusions were observed in keratinocytes during an ultrastructural investigation of the skin of hairless mice exposed to UVB radiation. Mice were irradiated 3 times a week for 5–6 months with sunlamps at individual doses seldom exceeding 0.06 J/cm2. Strips of dorsal skin were processed for electron microscopic examination; blocks were sectioned to include both epidermis and dermis. Mitochondrial inclusions were observed in keratinocytes of the basal, spinous and granular layers. They were spherical in shape and of moderate and homogeneous electron density. Mitochondria toward the upper regions of the epidermis were swollen and had fragmented cristae; mitochondria in the lower areas of the epidermis usually contained smaller and less dense inclusions and intact or partially disrupted cristae. Because mitochondria are essential in providing the energy for cellular function, keratinocyte mitochondrial damage induced by UVB radiation may have serious pathological consequences. Possible mechanisms involved in mitochondrial inclusion formation are suggested. Copyright © 1990, Wiley Blackwell. All rights reserved