Peroxidase technique for the detection of photochemical lesions in intracellular deoxyribonucleic acid

The widespread use of phototherapy for the prevention and treatment of neonatal hyperbilirubinemia has generated some conxern as physiologic substances other than bilirubin may be photoactivated. Little information is available on the long term toxicity of these photodecomposition products. Recent observations of the in vitro DNA-modifying activity of phototherapy lights has encouraged us to develop laboratory procedures which can identify and quantitate these light-induced alterations. The purpose of the present study was to develop a technique capable of detecting photochemical changes in the genetic material of human cells in tissue culture. The results demonstrate that the antinucleoside peroxidase staining procedure is capable of detecting changes in the DNA of human cells exposed to physiologic (riboflavin) and nonphysiologic (methylene blue) photosensitizing agents in the presence of light with a fluence rate (450 nm) of 141 muW-cm2.