| Abstract: | This experiment was carried out in order to investigate the time sequence of tissue fibrinolytic activity in human skin following UVB or UVA after topically applicated psoralen using Todd's technique of fibrinolytic autography. Tissue fibrinolytic activity increased in the upper dermis for one to six hours after exposure to psoralen and subseqent UVA, when erythema responses were absent. The return to a normal pattern of fibrinolysis occured in the upper dermis 12–18 hours after treatment with psoralen and UVA, and then psoralen-UVA-induced erythema responses began. These responses were maximal 96 hours after treatment with psoralen and UVA, although no fibrinolytic activity was found in the upper dermis. Little change was observed in the lower dermal activity throughout the course of these responses. After UVB irradiation, a transient increase in fibrinolytic activity occured, with a normal pattern of lysis returning in the lower dermis at 12–18 hours. In the lower dermis an increase was observed at one to 6 hours although the activity in the upper dermis had already decreased. UVB erythema responses appeared within this period, were maximal at 6–12 hours, and declined gradually after 12 hours concomitantly with the activity in the upper and lower dermis. The upper dermal activity disappeared at 18 hours, while the lower dermal activity was not found after 72 hours. |
