Effects of radiation of human-Chinese hamster somatic cell hybrids

Human fibroblast cells were exposed to 0, 10, 20 or 40 J/Kg of x-rays and then fused with unirradiated Chinese hamster cells deficient in HPRT. Cells were plated out in unirradiated MEM in 60mm petri dishes at a concentration of 2 x 104 cells/dish. Eighty dishes were used for each radiation treatment. Twenty-four hours after fusion the medium was replaced with selective medium containing thymidine, hypoxanthine, aminopterin and ouabain so that only hybrid cells could survive. Colonies derived from unirradiated human cells were seen earlier than those derived from unirradiated cells. Furthermore, the delay in appearance of hybrid cells increased, in a linear fashion, with increasing radiation dose. The number of dishes having no colonies was greater at higher radiation doses