Photosensitization of the lens by 8-methoxypsoralen

During the past decade, ambient ultraviolet radiation has been implicated in the age-related increase in fluorescence and pigmentation of the human lens nucleus. 8-Methoxypsoralen (8-MOP) (currently in vogue for the treatment of psoriasis) is a well-known photosensitizing agent. This drug lar fluorescence (360/440 nm.) and a change in receiving a single intraperitoneal dose (4 to 8 mg./kg.) of 8-MOP. When such rats are subjected to ambient light or ultraviolet (UV) radiation in vivo, there is an enhancement of lenticular fluorescence (360/440 nm.) and a change in their phosphorescence spectra. In vitro studies on lenses derived from rats given 8-MOP and exposed to monochromatic UV radiation show effects similar to those of the in vivo experiments. The foregoing studies demonstrate that 8-methoxypsoralen enters the lens and can be affected by ambient light as well as UV radiation, resulting in a photosensitized enhancement of lenticular fluorescence and a binding of this photosensitizing agent to macromolecules within the lens.