Effect of bromocriptine on the sensitivity of pituitary tumor cells to radiation.

GH3 cells, a PRL-secreting rat pituitary tumor cell line, are sensitive to bromocriptine, and provide a useful model for the present studies. GH3 cells, in the presence or absence of 2.5 x 10(-5) M bromocriptine, were irradiated at doses ranging from 0 to 10 Gy. After irradiation the bromocriptine was washed out, cells were seeded at a density of 10,000 cells/ml, and growth curves were obtained by counting the cell number at weekly intervals for 1 month. Cell growth was inhibited by the radiation in a dose-dependent fashion, with complete inhibition of cell growth by 9 Gy. However, no protection against radiation damage was afforded by bromocriptine. These results might suggest that the combined therapies of tumor shrinkage by bromocriptine and stereotactic irradiation of the sella might be a useful clinical therapeutic strategy, particularly in patients with large tumors, severe hyperprolactinemia, and pre-existing hypopituitarism.