IMMUNOHISTOCHEMICAL LOCALIZATION OF LYSYL OXIDASE IN NORMAL HUMAN SKIN

Lysyl oxidase (EC 1.4.3.13), a copper-dependent enzyme which catalyses the formation of aldehyde cross-links, and acts primarily on collagen and elastin, is known to be increased during wound healing and in fib rotic disorders including liver cirrhosis and atherosclerosis, and to be decreased in some hereditary connective tissue diseases and in mali gnant cell lines. A recent study showed that lysyl oxidase might posse ss tumour suppressor activity as an antioncogene for ras. Little is kn own about the localization of this enzyme in human skin. In this study , we determined immunohistochemically the localization of lysyl oxidas e in normal skin of young and elderly subjects obtained from sun-expos ed and unexposed regions of the body. All skin samples tested had simi lar distributions of lysyl oxidase. The enzyme was present both extrac ellularly and intracellularly. Extracellularly, a few granular aggrega tes of immunoreactants were observed along collagen and elastic fibres . These granules were more common in the adventitial portion of the de rmis than in the reticular portion. Of all sun-exposed and unexposed r egions studied, the skin of the face displayed the greatest amount of extracellular immunoreactants. Immunopositive granules were observed i ntracerlularly in fibroblasts, vascular endothelial cells, sweat gland s, sebaceous glands, arrector pill muscles and some keratinocytes. The se findings provide evidence that, as suggested in recent reports, lys yl oxidase may have a variety of intracellular functions.