Effects of bromocriptine on experimental GH3 cell tumors

Bromocriptine in concentrations up to 10(-4) M was studied for morphological and endocrinological effects upon the GH3 cell line as well as the GH1 and AtT-20 cell lines. The cells (10(5)/ml) were incubated with RPMI 1640 or in some experiments Dulbecco's Modified Eagle's Medium supplemented with 10% FCS. Bromocriptine was added in concentrations of 10(-4) to 10(-8) mol/L and aliquots of medium were obtained at 2 and 24 hs for the determination of growth hormone and prolactin. Significant reductions in concentrations of growth hormone and prolactin as well as cell number were observed with a concentration of bromocriptine of 10(-4) M at 24 hs. The electron microscopic appearance of GH3 cells treated with 10(-4) mol/L concentrations of bromocriptine for 24 hs demonstrated extensive and marked vacuolization in the cytoplasm which had already appeared 2 hs after treatment with bromocriptine. In bromocriptine-treated (10(-4) mol/L for 24 hs) GH1 cells and AtT-20 cells, the morphologic features were essentially unchanged, compared to the untreated group. Since many previous reports demonstrated a defective dopamine receptor system in GH3 cells, it must be concluded that bromocriptine has an extradopaminergic action which is selectively observed in GH3 cell.