Direct and indirect effects of UVA on skin vessel leakiness.

By using the suction blister technique we have investigated the leakiness of skin vessels in healthy volunteers after whole-body suberythemogenic doses of UVA radiation (a quadrant on one side of the abdominal skin was shielded with lead-rubber). The accumulation of intravenously injected labeled albumin in blister fluid was slightly elevated 1 day after irradiation and increased significantly 2 days later. The blister concentrations of 4 endogenous plasma proteins (albumin, transferrin, IgG, and alpha 2-macroglobulin) were elevated 1 day after radiation exposure and normalized 2 days later. All changes were equal on irradiated and nonirradiated skin. It is concluded that UVA radiation can induce a continued or biphasic increased leakage of plasma proteins in the skin vessels, due to a humoral rather than to a direct physical effect of the radiation on the vessel walls. It is suggested that an increased microvascular leakiness in organs other than the skin might be present.