Objectives: To analyze the common allele frequencies of the arylamine-N-acetyltransferase 1 (NAT1) and examine the relationship between genotype and phenotype in a Thai population.
Methods: Peripheral blood samples from 233 Thai individuals were analyzed for genotype using polymerase chain reaction with restriction fragment-length polymorphism assays and for phenotype by determination of NAT1 enzyme kinetics in leukocytes using para-aminobenozic acid as a specific substrate.
Results: Of 466 NAT1 alleles assayed, the frequency of the NAT1*4 allele (wild-type) was 0.504 (95%CI 0.458-0.551) and those of the NAT1*10, *3 and *11 alleles were 0.438 (0.392-0.484), 0.034 (0.02-0.055) and 0.024 (0.012-0.042), respectively. Neither NAT1*14A nor *14B alleles were found in this studied population. The activity of NAT1 enzyme from peripheral blood leukocytes determined in 47 subjects was found to vary widely. The intrinsic clearance and Vmax values of NAT1 enzymes with genotypes NAT1 *4/*4, *10/*10 and *4/ *10 were not significantly different.
Conclusion: The frequency distribution of the major NAT1 alleles in the Thai population has a similar pattern to some Asian populations; however, racial differences among Asian populations need further clarification.