The British Journal of Radiology, Vol 59, Issue 699 257-261, Copyright © 1986 by British Institute of Radiology

ARTICLES

Dose-response relationships for photodynamic injury to murine skin

JV Moore, JP Keene and EJ Land

Oedema and necrosis of murine tail skin have been measured after intravenous injection of haematoporphyrin derivative ("Photofrin", or PhI) followed 24 h later by graded exposures of the tail to full-spectrum visible light from a quartz-halogen lamp. End-points were degree of oedema and the proportion of mice in a dose-group that developed skin necrosis and tail atrophy. Oedema developed within 24 h of illumination and was a function of PhI dose and duration of light exposure. Onset of necrosis occurred after a minimum of 5 days and onset time was an inverse function of exposure time. Probit plots of proportion of necroses versus light exposure yielded values for ND50 (exposure corresponding to 50% incidence of necrosis) and l/slope. At the high but non-toxic dose of 2 mg PhI/mouse, ND50 was 18 min, l/slope 4 min, for pigmented BDF1 mice. Halving the PhI dose increased ND50 by a factor of 1.9. Albino BALB/c mice were markedly more sensitive to 2 mg PhI plus light than BDF1 mice: the ND50 was 7 min. Temporary occlusion of the blood supply to the tail (10 min before and during illumination) abrogated totally the oedematous and necrotic reactions to photodynamic therapy.