Evidence for the presence of dopamine D1 receptor mRNA and binding sites in monkey amniotic epithelial cells

In this study we examined the presence of dopamine D1 receptors in monkey amniotic epithelial cells (MAEC) using RT-PCR and radioligand binding experiments. We found that MAEC express D1 receptor mRNA that is having 99% homology with human dopamine D1 receptors. Saturation binding studies using [3H]SCH-23390 showed a high affinity D1 site with K(D) and Bmax values of 0.82 +/- 0.12 nM and 20.77 +/- 4.22 fmol/mg protein, respectively. Competition experiments showed that selective D1, but not D2, antagonists are potent displacers of [3H]SCH 23390 binding with a rank order of potency that is consistent with the pharmacology of the dopaminergic D1 site. These data provide, for the first time, compelling evidence that MAEC natively express D1 mRNA and binding sites and suggest that it may be a potential primate cell model to study D1 receptors and to explore new selective drugs active at these receptors.