POSSIBLE ASSOCIATION OF CATECHOLAMINE TURNOVER WITH THE POLYMORPHIC (TCAT)(N) REPEAT IN THE FIRST INTRON OF THE HUMAN TYROSINE-HYDROXYLASE GENE

Five allelic fragments were typed by a PCR-based process with a pair o f primers specific for the polymorphic sequence due to (TCAT)n tetranu cleotide repeat, a microsatellite repeat, in the first intron of the h uman tyrosine hydroxylase gene, i.e. A1, A2, A3, A4 and A5. Comparison s of some neurochemical parameters of the catecholamine pathway were t hen made between the unrelated individuals genotypically classified in to six subgroups, five homozygotic and one heterozygotic. Among the si x subgroups, the individuals with the A2/A2 genotype had the highest l evels of serum noradrenaline and those with the A4/A4 genotype had the lowest, and the individuals with the A1/A1 genotype;had; the highest levels of serum homovanillic acid. These findings suggest that polymor phism of the (TCAT)n repeat in the first intron of the human tyrosine hydroxylase gene may be associated with catecholamine turnover. Possib ly, the two alleles, A2 and A4, may be related to the high and low exc itabilities of the noradrenergic nerves, respectively, and the allele, Al, may be associated with the up-regulation of dopamine turnover.