EXPRESSION OF A HIGH-AFFINITY SEROTONIN TRANSPORTER IN HUMAN-LYMPHOCYTES

This study was undertaken to assess the capability of lymphocytes to a ctively transport serotonin (5-HT). The data we obtained showed that l ymphocytes isolated from the blood of normal human subjects contained a high-affinity uptake system for [H-3]5-HT. Kinetic analysis of the u ptake data as computed by regression analysis from Lineweaver - Burk p lots, yielded a K-m of 180 +/- 20 nM and V-max of 94 +/- pmole/10(7) c ells. The uptake of [H-3]5-HT was temperature, sodium and chloride dep endent and was potently inhibited by the antidepressants clomipramine, imipramine, fluoxetine and fluvoxamine, which are specific for the 5- HT transporter. Compounds that are more selective for norepinephrine a nd dopamine transporters such as mazindol, desipramine, and GBR 19209 had a lower inhibitory effect on the uptake of [H-3]S-HT in human lymp hocytes. The expression of a 5-HT transporter in human lymphocytes tha t resembles 5-HT uptake by platelets and brain synaptosomes may provid e insights into the potential role of 5-HT in immune function and its relationship to the neurobiology of affective and addictive disorders.