CONCORDANCE BETWEEN ENZYME-ACTIVITY AND GENOTYPE OF GLUTATHIONE-S-TRANSFERASE-THETA (GSTT1)

Blood samples from 140 healthy German volunteers were used to further characterize the genetic polymorphism of the human theta class glutath ione S-transferase 1 (GSTT1). For measurements of GSTT1 activity, hemo lysates were incubated in vitro with different concentrations of dichl oromethane. The resulting enzymatically mediated production of-formald ehyde was determined colorimetrically by the Nash reaction. GSTT1 geno typing was performed by polymerase chain reaction (PCR) methods using genomic DNA from total white blood cells. The prevalence of homozygous deletion of the GSTT1 gene was 19.3% (95% confidence limits: 12.2-27. 7%). There was a high agreement between genotyping and phenotyping dat a. The individuals with the null genotype had a rate of formaldehyde p roduction below the limit of quantification. In addition, in the group of GSTT1-positive individuals, we could differentiate highly active p eople (35.7%) from individuals with an intermediate enzyme activity (4 5.0%). It can be concluded that the PCR method is suitable to quickly genotype large populations, whereas the phenotyping assay at present o ffers the advantage of differentiating heterozygously from homozygousl y active subjects. Our results confirm the ethnic differences in the p revalence of the homozygous deleted genotype which were previously obs erved and seem to exist even between closely related ethnic groups suc h as German and Swedish populations. (C) 1998 Elsevier Science Inc.