Effects of several agents on UVB- and UVA plus systemic fluoroquinolone-induced erythema of guinea pig skin evaluated by reflectance colorimetry.

The aim of this study was to clarify the mechanisms underlying the erythema of guinea pig skin induced by ultraviolet (UV) irradiation alone and in combination with a systemic fluoroquinolone (FQ). The effects of several drugs which may modify the actions of some inflammatory mediators and radicals possibly released in the inflamed site on the erythema were examined and compared in an objective and quantitative way by measuring the change in color of the irradiated skin, determined as the change in chroma (C*) with use of reflectance colorimetry. After confirming that the C* value increased in an irradiation dose-dependent manner and reached a plateau 1-2 h after irradiation of UVB alone or UVA coadministered with an FQ, Y-26611 (10 mg/kg, i.p.), guinea pigs were pretreated with indomethacin, butylated hydroxytoluene (BHT) or beta-carotene before, or treated with H1- or H2-receptor antagonist, superoxide dismutase or N omega-nitro-L- arginine methyl ester after UV irradiation, and their inhibitory effects against erythema were evaluated. It was suggested that there are some substantial differences between UVB- and UVA plus FQ-induced erythemas. Although histamine makes little contribution to both types of erythema, metabolites of arachidonic acid catalyzed by cyclooxygenase contribute more to UVB-induced erythema, whereas superoxides take more part in UVA plus FQ-induced erythema. Furthermore, nitric oxide seems to participate in both types of erythema; however, the pretreatment with BHT or beta-carotene was ineffective against both erythemas. From these results, interventions should be directed to powerfully scavenging radicals for prevention and treatment of UV plus FQ-induced phototoxicity.