Evidence of dopamine D1 receptor mRNA and binding sites in cultured human amniotic epithelial cells

In this study, we employed RT-PCR and radioligand binding studies to evaluate the gene expression and binding characteristics, respectively, of dopamine D(1) receptors in human amniotic epithelial cells (HAEC). The results showed that HAEC natively expressed D(1) receptor mRNA, as measured by RT-PCR, which was identical to that of human brain. Saturation binding studies using [(3)H]SCH 23390 demonstrated the presence of a high affinity D(1) site in HAEC with K(D) and B(max) values of 2.01+/-0.25 nM and 32.5+/-3.7 fmol/mg protein, respectively. Competition studies showed that selective D(1) antagonists were potent displacers of [(3)H]SCH 23390 binding with a potency order consistent with D(1) receptor characteristics. The current results present compelling evidence that HAEC natively express D(1) receptor mRNA and binding sites. The results also establish a primate cell model that can possibly be used for studying D(1) receptor signal transduction and molecular mechanisms and exploring newly developed drugs acting at these receptors.