Unscheduled incorporation of thymidine in ultraviolet-irradiated human lymphocytes.
The nature, degree, and kinetics of unscheduled thymidine incorporation previously shown to occur in 90 % of irradiated lymphocytes was stud-incorporation was sever ely depressed i n t h e presence of 10(-4) M acriflavine and by low temperature, but was unaffected by 10(-3) M hydroxyurea or caffeine. Over a dose range of 25 to 400 ergs/mm2, the uptake of thymidine was increased by a factor of only 1.6, although the survival of lymphocytes, measured 5 days after irradiation, decreased by almost two orders of magnitude. (The survival curve suggests that 90% of the lymphocytes have a D0 of 35 ergs/mm(2) and 10 % have a D0 of 250 ergs/mm(2).) After exposure to 25 ergs/mm(2), over 70 % of the cells survived for 5 days in culture; moreover, cells which had been stimulated by this dose to incorporate thymidine transformed and divided after exposure to phytohema-glutinin. The final uptake of thymidine was significantly greater when a total dose of 75 ergs/mm(2) was fractionated into three doses of 25 ergs/mm(2) given at six hourly intervals than when it was given as a single dose. The degree of thymidine incorporation and the fraction of leukemic cells labeled were not significantly different from those in normal lymphocytes.
Evans
R G
RG
Biophysics Division, Sloan-Kettering Cancer Institute, New York, New York, USA.
Norman
A
A
D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism* / Q000528:radiation effects*; D004260:DNA Repair / Q000502:physiology*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism* / Q000528:radiation effects*; D011829:Radiation Dosage; D013936:Thymidine / Q000493:pharmacokinetics*; D014466:Ultraviolet Rays
D004247:DNA; D013936:Thymidine