Correlation between serotonin uptake in human blood platelets with the 44-bp polymorphism and the 17-bp variable number of tandem repeat of the serotonin transporter.

Dysfunctions of the central serotonin (5-hydroxytryptamine, 5-HT) system seem to be associated with psychiatric disorders such as schizophrenia or depression. Previous studies suggested that a 44-bp insertion/deletion polymorphism of the 5-HT transporter (5-HTT) promoter region might influence the transcriptional activity of the 5-HTT gene, and the insertion variant resulted in increased 5-HTT expression and 5-HT uptake. Moreover, a 17-bp variable number of tandem repeat (VNTR) polymorphism of the second intron may act as a transcriptional regulator with allele dependent differential enhancer-like properties. Since the 5-HTT of human platelets shares many properties with the transporter of neural tissue, platelets are widely used as a surrogate tissue source, possibly reflecting central 5-HT metabolism. Therefore, we investigated the impact of the 44-bp polymorphism and the 17-bp VNTR for 5-HT uptake in platelets of 50 male subjects. We found no significant effect of the 44-bp polymorphism and of the 17-bp VNTR on maximum rate (Vmax) of 5-HT uptake. However, individuals homozygous for the 5-HTT intron 2 allele with 12 repeats (STin2.12) of the 17-bp VNTR appeared to have lower affinity of 5-HT uptake than individuals heterozygous for the STin2.10/STin2.9 allele. This was also observed for the combined analysis of both polymorphisms. In conclusion, we found no association between the different genotypes of the 44-bp polymorphism and the 17-bp VNTR and maximum rate of 5-HT uptake into platelets.