Characterization of 5-HT transporter and receptor system in HeLaS3 cells by [3H]8-OH-DPAT and other serotonergic ligands

[3H]8-OH-DPAT is a selective ligand for labeling 5-HT1A receptor sites. In competition binding experiments, we found that classic biogenic amine transporter inhibitors displaced [3H]8-OH-DPAT binding at its high-affinity binding sites in HeLaS3 cells. [125I]RTI-55 and [3H]paroxetine are known to specifically label amine transporter sites, and this was observed in our cells. Displacement studies showed that 8-OH-DPAT displayed affinity in a dose-dependent manner for the labeled amine transporter sites. These data suggest that [3H]8-OH-DPAT binds to amine uptake sites in HeLaS3 cells. A variety of drugs targeting different classes of receptors did not significantly affect [3H]8-OH-DPAT binding. Moreover, we determined the specific binding effects of various serotonergic ligands (i.e. [125I]cyanopindolol, [3H]ketanserin/[3H]mesulergine, [3H]GR-65630, [3H]GR-113808 and [3H]LSD) that specifically labeled 5-HT1, 5-HT2, 5-HT3, 5-HT4 and 5-HT5–7 receptors, respectively. It is suggested that HeLaS3 cells contain distinct types of the related to 5-HT receptor recognition binding sites. These observations could help elucidate the relevant characteristics of different types of 5-HT receptors and 5-HT membrane transporters in tumor cells and their role in tumorigenesis.