PROTEIN-BIOSYNTHESIS IN LOW-DOSE IONIZING RADIATION-ADAPTED HUMAN-MELANOMA CELLS

Adaptive responses induced by low dose gamma-ray irradiation in human melanoma cells were examined using a clonogenic assay, Survival fracti ons were significantly increased in cells irradiated with low dose gam ma-rays then 4 hrs later with high dose y-ray as compared to cells irr adiated only with high dose gamma-rays. When low dose irradiation was given 20 hrs prior to high dose irradiation, however, no adaptive resp onse was induced. Changes in protein biosynthesis in human melanoma ce lls were observed under the same conditions. Significant changes in pr otein biosynthesis occurred in the nuclear and membrane proteins of ce lls first irradiated with a low dose then a high dose of gamma-rays af ter 4 hrs. No such changes were found in cells irradiated with low dos e gamma-rays 20 hrs prior to high dose irradiation, consistent with th e results of the clonogenic assay. Our findings suggest that prior tre atment with low dose gamma-rays induces an adaptive response that has a significant effect on the induction of the nuclear and membrane prot ein biosynthesis caused by high dose y-ray irradiation of human melano ma cells.