Characterization of dopamine D2 receptor gene expression and binding sites in human placenta amniotic epithelial cells

This study was to investigate the presence of dopamine (DA) D-2 receptors mRNA and binding sites in human amniotic epithelial cells (HAEC). RT-PCR revealed that HAEC express DA D-2 receptor mRNA that is having 100 per cent homology with human DA D-2 receptors. Radioligand saturation binding studies showed a [H-3]YM-09151-2 high affinity binding site with a K-D and B-max values of 0.53+/-0.09 nm and 119.6+/-8.5 fmol/mg protein, respectively. Competition experiments demonstrated that selective D-2 antagonists such as spiroperidol, domperidone and eticlopride potently competed with [H-3]YM-09151-2 binding, whereas selective D-1 antagonists like SCH 23390 displayed weaker competition for the binding sites. The rank order of potency of these compounds in competing with [H-3]YM-09151-2 for the binding sites was consistent with the pharmacology of the DA D-2 receptors. All competition curves were better fitted to a one-site model with a Hill coefficient around unity, indicating that [H-3]YM-09151-2 is labelling a single population of receptors. These results provide evidence that HAEC natively express DA D-2 receptor mRNA and binding sites. Although the physiological function of D-2 receptors in HAEC is currently unclear, the present results suggest that these cells could represent a source of human DA D-2 receptors without transformation or cloning procedures. (C) 2003 Elsevier Science Ltd. All rights reserved.