Abstract
Ultraviolet radiation is considered to be the most harmful part of solar
energy affecting man. The depletion of the ozone layer around the Earth
increases the total exposure to UV-light. The incidence of skin cancer in
man has been shown to be associated with exposure to solar radiation,
especially to UV-light. UV is capable of initiating skin carcinogenesis
through DNA damage, particularly by formation of DNA photoproducts. The
major products formed by UV irradiation are dipyrimidine compounds,
namely cyclobutane dimers and 6-4 photoproducts. A high mutation
frequency at pyrimidine sites in skin tumours provides additional
evidence for the relationship between UV-induced DNA damage and skin
cancer.
The research program was focused on the development and application of a
highly specific and sensitive 32P-HPLC method for the study of UV-induced
DNA damage in humans.
* The application of the developed method to human studies demonstrated
that one minimal erythema dose of solar- simulated radiation is
capable of inducing levels of DNA damage far exceeding any other
known external exposure. This finding may explain the high frequency
of skin cancer among other tumours
* There is a large interindividual variation in the induction of
photoproducts after exposure to a uniform physical dose of solar-
simulated radiation
* There is no association between erythemal response and induction of
DNA damage
* The reparability of dipyrimidine lesions dependent on the
dipyrimidine pair forming a lesion, implicating sequence-specificity
of the repair process
* There is a large interindividual variation in the rates of DNA repair
process.
Taken all our results together, we have shown that human response to
solar- simulated radiation is highly individual. The level of immediate
damage may vary for a given acute biological dose and repair rates may
vary. At present, we have no evidence that these two aspects are coupled
in any way. Thus, a combination of proneness to damage along with poor
repair may predispose individuals to skin cancer.
