PREVALENCE OF HOMOZYGOSITY FOR THE DELETED ALLELES OF GLUTATHIONE-S-TRANSFERASE-MU (GSTM1) AND GLUTATHIONE-S-TRANSFERASE-THETA (GSTT1) AMONG DISTINCT ETHNIC-GROUPS FROM BRAZIL - RELEVANCE TO ENVIRONMENTAL CARCINOGENESIS

Environmental related diseases due to occupational carcinogens and tox ic substances are a serious problem particularly in developing countri es. The glutathione S-transferase system is fundamental for the detoxi fication of numerous carcinogens and mutagens. The individual inherite d susceptibility to chemical carcinogenesis due to glutathione S-trans ferase mu (GSTM1) and theta (GSTT1) varies significantly among distinc t ethnic groups. In this study we determined the prevalence of the nul l genotype of the GSTM1 and GSTT1 genes among individuals from three d istinct Brazilian racial groups using a multiplex-PCR methodology. The results showed that the highest prevalence of the null genotype for t he GSTM1 occurred among Caucasians (55%, allele frequency = 0.74), fol lowed by 33% among Brazilian Black subjects (allele frequency = 0.57), and 20% among Amazonian Indians (allele frequency = 0.45). For GSTT1 a homogenous distribution of the null genotype was found among Caucasi an and African descendants (18.5 and 19% homozygotes, respectively, al lele frequency = 0.43), with a lower prevalence among Amazonian Indian s (11% of homozygotes, allele frequency = 0.34). Whether the deficienc y of the GST system contributes to a predisposition to environmental r elated carcinogenesis in specific populations in Brazil remains to be determined.