STABLE EXPRESSION OF HUMAN D3 DOPAMINE-RECEPTORS IN GH4C1 PITUITARY-CELLS

Human D3 dopamine receptor DNA was stably transfected into GH4C1 pituitary cells. Displacement of iodosulpiride binding in hD3 transfected cells (K(d) = 0.3 nM, B(max) = 89 fmol/mg protein) by dopaminergic ligands was indistinguishable from that of hD3 receptors in CHO cells. Only two clonal cell lines exhibited weak GppNHp-dependent shifts in [H-3]N-0437 binding, and these were used for functional assays. Neither arachidonic acid metabolism, cAMP levels, inositol phosphate turnover, intracellular calcium, or potassium currents were consistently affected by dopamine (1-10 muM). The paucity of responses indicates that human D3 receptors do not couple efficiently to these second messengers in GH4C1 cells.