Cyclobutane thymidine dimers are present in human urine following sun exposure: quantitation using 32P-postlabeling and high-performance liquid chromatography

J Invest Dermatol. 2001 Aug;117(2):263-8. doi: 10.1046/j.1523-1747.2001.01416.x.


Cyclobutane thymidine dimer (T=T) is the major DNA photoproduct formed in human skin after solar radiation. We have developed a 32P-postlabeling method suitable for quantitating T=T in human urine with a detection limit of about 0.5 fmol per 10 microl urine. The method was used in the present study to measure the daily T=T urinary level of two volunteers over a 15 d period, including frequent sun exposures ranging from 0 to 5 h daily. T=T was not detected before or immediately (4 h) after the initial sun exposure but was first observed in urine samples collected 18 h after the initial exposure. Thereafter, urinary T=T levels gradually increased up to a peak reached about 3 d after the maximum sun exposure. The levels decreased during the following days but were still detectable 8 d after the last sun exposure. About 70-75% decrease in excreted T=T was observed after 8 d. The T=T levels measured in urine were lower but in the same order of magnitude as the levels expected after a theoretical calculation based on previous published results and reasonable assumptions. This study shows the occurrence of cyclobutane thymidine dimers in human urine after skin exposure to solar radiation.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Chromatography, High Pressure Liquid / methods*
  • Creatinine / analysis
  • Creatinine / urine
  • DNA / radiation effects
  • Dose-Response Relationship, Radiation
  • Female
  • Humans
  • Male
  • Phosphorus Radioisotopes
  • Pyrimidine Dimers / analysis*
  • Pyrimidine Dimers / urine*
  • Skin / radiation effects*
  • Sunburn / diagnosis*
  • Sunburn / urine
  • Sunlight / adverse effects*


  • Phosphorus Radioisotopes
  • Pyrimidine Dimers
  • DNA
  • Creatinine