PIXE analysis in uninvolved skin of atopic patients and aged skin.

PIXE (proton-induced X-ray emission) analysis was used to determine the elemental distribution in normal-appearing skin of patients suffering from atopic eczema and in the skin of elderly people. With this technique, elements with atomic numbers greater than or equal to 14 can be detected simultaneously in cryosections of skin biopsies down to a concentration of 1 ppm. Compared with a control group, the epidermal concentrations of Zn and Cu, which are constituent parts of a variety of enzymes, were increased in uninvolved skin of patients with atopic eczema. An increased concentration of these two metals might indicate that even in the epidermis of clinically normal skin of atopic patients, the content of certain enzymes is increased. In the epidermis of elderly people the level of K was lower and that of Ca was higher than in the epidermis of a younger age group. The decreased K level may reflect a reduction of the intracellular volume in the epidermis of aged skin. As high Ca concentrations inhibit the proliferation of and promote the differentiation of keratinocytes, elevated Ca levels may be of importance for the age-associated decrease in epidermal turnover rate.