||Serotonin transporter promoter variants in autism: Functional effects and relationship to platelet hyperserotonemia.
We have examined the effects of the serotonin transporter gene (5-HTT, locus SLC6A4) promoter polymorphism (5-HTTLPR) on platelet 5-HT physiology in autism. Platelet 5-HT uptake rates and affinities (V-sub(max) and K-sub(m)), uptake site densities (B-sub(max)) and 5-HT levels were examined in 31 French individuals with autism genotyped with respect to the 5-HTTLPR. Platelet 5-HT uptake and 5-HT levels were measured using HPLC; uptake sites were determined by radioligand binding. A 1.5-fold increased rate (V-sub(max)) of platelet 5-HT uptake was observed in II genotype individuals compared to those with is and ss genotypes. Although median levels of platelet 5-HT in platelet-rich plasma were higher in the II group, only trend level significance was observed; platelet 5-HT content measured in whole blood was similar across genotypes. Correlations between uptake and platelet 5-HT levels and between B-sub(max) values and 5-HT levels were somewhat lower. Based on these preliminary data and prior studies of allele frequencies, we conclude that the 5-HTTLPR is not a major determinant of the group mean platelet serotonin elevation seen in autism. (PsycINFO Database Record (c) 2007 APA, all rights reserved)