The ultrastructure of the interfollicular epidermis of the hairless (hr/hr) mouse. V. The cytoplasm of the horny cells

The effects of topical and oral L-selenomethionine on pigmentation and skin cancer induced by ultraviolet irradiation

This study was conducted to determine whether oral and/or topical selenium (Se) supplementation can reduce the incidence of acute and/or chronic damage to the skin (i.e., sunburn and pigmentation and/or skin cancer, respectively) induced by ultraviolet (UV) irradiation in mice. Groups of 38 BALB:c female mice or 16 Skh:2 hairless pigmented mice were treated with 1) lotion vehicle, 2) 0.02% L-selenomethionine (SeMet) lotion, or 3) vehicle and 1.5 ppm SeMet in the drinking water. Within each group, 30 BALB:c mice or 12 Skh:2 mice were given UV irradiation (Westinghouse FS 40 bulbs) three times per week in doses of 0.575 and 0.24 J/cm2, respectively. The animals' weights and food intakes and the Se concentrations of skin and liver were measured. Skin biopsies were taken from the backs and abdomens of all animals to evaluate the relative amounts of Se and the damage by UV irradiation. Skin pigmentation was scored, and the total number of clinically detectable skin tumors per animal was counted weekly. Results showed that the skin Se concentrations in areas of application of the lotion containing SeMet were greater than those of animals given comparable oral doses, while the Se concentrations of untreated skin and liver were similar to those of animals receiving oral Se. Mice treated with Se showed no signs of toxicity and had significantly less skin damage by UV irradiation, as indicated by reduced inflammation and pigmentation and by later onset and lesser incidence of skin cancer.

Sunscreens prevent ultraviolet photocarcinogenesis

Sunscreens of low or high sun protection factors (SPF*) were tested for their ability to inhibit ultraviolet (UV) carcinogenesis in two varieties of hairless mice. Low protection (SPF = 2) reduced by 50% the number of albino animals developing tumors. High protection (SPF =15) prevented tumor formation. Tumorigenesis was totally prevented in the lightly pigmented variety with either sunscreen, demonstrating the added protection of melanin. In mice and man, UV-induced cancer is a cumulative process. Reducing the amount of UV light reaching the basal layer will retard that process.