Abstract
Human embryonic kidney 293 (HEK-293) cells stably transfected with the human serotonin (5-HT) or dopamine transporter (hSERT, hDAT), or the rat GABA transporter GAT-1 were incubated with saturating concentrations of transporter substrates (hSERT: [(3)H]5-HT, [(3)H]N-methyl-phenyl-pyridinium (MPP+); hDAT: [(3)H]dopamine, [(3)H]MPP(+); rGAT: [(3)H]GABA). Uptake velocities decreased significantly over time for [(3)H]5-HT and [(3)H]dopamine (already visible at 1 min), but not for [(3)H]MPP(+) or [(3)H]GABA. In efflux experiments cells were preloaded and substrate diffusion into the medium was studied following the addition of appropriate uptake inhibitors. Fractional effluxes were (% min(-1)) 1.27, 0.72, 0.27 and 0.08 for [(3)H]5-HT, [(3)H]dopamine, [(3)H]MPP(+) and [(3)H]GABA, respectively. The results suggest that in uptake experiments the more lipophilic substrates [(3)H]5-HT and [(3)H]dopamine leave the cells by diffusion already after a short time (1 min) of accumulation.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
1-Methyl-4-phenylpyridinium / metabolism
-
Animals
-
Carrier Proteins / biosynthesis*
-
Cell Line / metabolism*
-
Diffusion
-
Dopamine / metabolism
-
Dopamine Plasma Membrane Transport Proteins
-
GABA Plasma Membrane Transport Proteins
-
Humans
-
Kidney
-
Membrane Glycoproteins / biosynthesis*
-
Membrane Proteins / biosynthesis*
-
Membrane Transport Proteins / biosynthesis*
-
Nerve Tissue Proteins*
-
Neurotransmitter Uptake Inhibitors / metabolism*
-
Organic Anion Transporters*
-
Rats
-
Serotonin / metabolism
-
Serotonin Plasma Membrane Transport Proteins
-
gamma-Aminobutyric Acid / metabolism
Substances
-
Carrier Proteins
-
Dopamine Plasma Membrane Transport Proteins
-
GABA Plasma Membrane Transport Proteins
-
Membrane Glycoproteins
-
Membrane Proteins
-
Membrane Transport Proteins
-
Nerve Tissue Proteins
-
Neurotransmitter Uptake Inhibitors
-
Organic Anion Transporters
-
SLC6A1 protein, human
-
SLC6A4 protein, human
-
Serotonin Plasma Membrane Transport Proteins
-
Slc6a1 protein, rat
-
Slc6a4 protein, rat
-
Serotonin
-
gamma-Aminobutyric Acid
-
1-Methyl-4-phenylpyridinium
-
Dopamine