The Mechanism for Serotonine Re-uptak by Heterologous Expressed Human Serotonine Transporter in Xenopus Oocyte

Abstract: cRNA of SERT was transcribed from cDNA， which was cloned in the pOTV vector. Oocytes of Xenopus laevis were injected with transcribed cRNA in vivo and turned to a heterologous expression model (human serotonin transporter， hSERT) in 5_6 days. With voltage clamp technique in recording the current induced by 5-HT， we tested the function of the expressed 5-HT transporter and studied factors which influence the re-uptake of hSERT. When the cell membrane potential was held at _60 mV and perfused with Ringer''s solution containing 5-HT， a steady inward current appeared and was almost completely inhibited by specific 5-HT transporter blocker， Desipramine， which demonstrated that it was 5-HT-induced current. The 5-HT-induced current varied with holding potentials or voltages in step protocol. The more negative of the clamping voltage， the bigger of the 5-HT-currents. The results from the experiments with 0 mmol/L Na+ or 0 mmol/L Cl_ in Ringer solution indicated that transporting of 5-HT required Na⁺ and Cl_ ion in extra-cellular solution and the influences of Na⁺ and Cl_ ion on transporting were different， for with 0 mmol/L Na+ or 0 mmol/L Cl_ the currents were reduced by (89.6±1.4)% and (51.7±1.5)% respectively. As the concentration of 5-HT in the perfusing Ringer's solution increased from 0.1 to 15 mmol/L， the current augmented accordingly until it was saturated. Injection of 5-HT into the Oocyte making the intracellular concentration of 5-HT increased to about 20 or 40 folders， the 5-HT-induced current was not changed in spite of the changes of intracellular concentrations of 5-HT. Conclusion: Na⁺ ion and Cl_ ion are co-transported with 5-HT. The cell membrane potential may influence the 5-HT-induced current fulfilling a rapid regulation for re-uptake of 5-HT. Changing the intracellular concentration of 5-HT does not influence the amplitude of transporter current.
    

CSTR: 32200.14.cjcb.2006.06.0028