Distribution of glutathione S-transferase T1 phenotypes in the Estonian population

The distribution of glutathione S-transferase T1 (GSTT1) phenotypes was studied in a total sample of 673 Estonians whose four grandparents were born in Estonia, by an ELISA test able to differentiate between GSTT1 positive and GSTT1 negative phenotypes. 18% of the total sample did not present GSTT1-1 protein in whole blood. GSTT1-1 concentration was assayed in 519 out of the 552 GSTT1 positive subjects (i.e. 82% of the total sample). 49% percent of this subsample made up by 519 subjects was found to have GSTT1-1 in intermediate concentration and 33% in high concentration. The gene frequency of the GSTT1 deleted allele was estimated to be 0.423 as the square root of the frequency of the GSTT1 negative subjects (root 0.18 = 0.423) and that of the GSTT1 positive allele as (1-0.423) = 0.577. Statistically significant regional differences were found within the population with the lowest frequency of GSTT1 negative in western Estonia (9.5%) and the highest in the southeastern part of the country (24.5%).