The bilirubin-induced photodegradation of deoxyribonucleic acid.

The widespread use of phototherapy for neonatal jaundice has caused some concern since little is known about the cellular consequences of such treatment. The present study was undertaken to determine the effects of photoactivated bilirubin on the structure of purified deoxyribonucleic acid. DNA illuminated in the presence of bilirubin exhibited altered physical chemical properties as evidence by (1) a changed thermal helix coil transition profile, (2) a sensitivity of the treated DNA to alkaline degradation, and (3) a limited depolymerization of single-stranded DNA. The above changes were observed with a total light dosage representing only 5% of that received by a newborn infant during a 24-hr period of phototherapy in our nursery. In view of the known relationship between ability to modify cellular DNA and mutagenic and/or carcinogenic potential, the present results suggest that phototherapy is a complex process which may have potentially dangerous sequelae.