Long-Term Toxicity of Oral 8-Methoxypsoralen Plus Ultraviolet Radiation in Mice

AbstractThe combined effects of 8-methoxypsoralen (8-MOP) and ultraviolet radiation (UVR) in a photosensitizing protocol (psoralen-UVA, PUVA) were studied in hairless albino mice. The psoralen was administered orally by a pulse-feeding technique in which fasted mice were provided access to psoralen-containing feed. The mice were then exposed to radiation sources consisting of flurorescent “blacklight” lamps (F74T12 PUVA, Sylvania) either with or without an intervening filter designed to eliminate shortwave (UVB, λ < 320 nm) radiation. Exposure intervals were selected so that the total amount of ultraviolet A (UVA, λ 320–400 nm) delivered by the two configurations was equal (2 J/cm2). A series of dietary levels of 8-MOP provided mice with 0, 100, 250, and 625 mg/kg of diet. Neither radiation source, nor any tested 8-MOP level, produced grossly evident cutaneous damage, produced carcinogenesis, or reduced survival. In combination with either source, there was a consistent dosage-dependent enhancement of car...