The effect of various amino acids and drugs on the para- and meta-hydroxyphenylacetic acid concentrations in the mouse caudate nucleus.
Injection of L-p-tyrosine (800 mg/kg, 2 h) increased the mouse striatal para-hydroxyphenylacetic acid (p-HPAA) concentrations. A smaller dose of D,L-m-tyrosine (20 mg/kg, 2 h) produced a larger increase in mouse striatal meta-hydroxyphenylacetic acid (m-HPAA) concentrations. The administration of L-phenylalanine to mice caused a slight increase in the p-HPAA concentration in the corpus striatum after 2 h while a larger dose of L-phenylalanine (800 mg/kg) produced a greater increase. Eight hours following L-phenylalanine injection, p-HPAA concentrations were still elevated. With D-phenylalanine a significant increase was observed at eight hours after drug administration. Two drugs which reduce dopamine synthesis, alpha-methyl-para-tyrosine and apomorphine, decreased m-HPAA striatal concentrations without affecting p-HPAA concentrations. From these results, it is proposed that tyrosine hydroxylase activity determines p-HPAA concentrations by regulating p-tyrosine availability. This enzyme may also synthesize m-tyrosine which is subsequently decarboxylated to form m-tyramine and then oxidatively deaminated to form m-HPAA.
D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D010648:Phenylacetates / Q000378:metabolism*; D010649:Phenylalanine / Q000494:pharmacology; D014443:Tyrosine / Q000494:pharmacology
D000596:Amino Acids; D010648:Phenylacetates; C008070:4-hydroxyphenylacetic acid; D014443:Tyrosine; D010649:Phenylalanine; C008069:3-hydroxybenzeneacetic acid; D001058:Apomorphine