Effects of 3,4-dihydroxyphenylpyruvic acid and L-glutamic acid on some pharmacokinetic parameters of L-dopa in the rat.
In the rat, various oral doses of 3,4-dihydroxyphenylpyruvic acid (DHPPA) administered simultaneously with L-dopa were shown to elevate the serum L-dopa and cerebral dopamine concentrations dose-dependently. With increasing DHPPA: L-dopa ratio the L-dopa-sparing effect became greater. Although oral and intravenous doses of DHPPA showed that it was readily converted to L-dopa in the serum, only small amounts of dopamine (DA) were detected in the brain. The high 3-O-methyldopa concentrations, measured in the serum after DHPPA administration, might be responsible for the failure of the L-dopa formed to pass the blood-brain barrier. Concomitant administration of L-dopa and glutamic acid gave significantly higher L-dopa values in the serum and DA and homovanillic acid values in the brain than did the same dose of L-dopa alone. This indicates that the transamination of L-dopa can also be effected by coadministration of L-dopa and an amino group donor in vivo.
D000818:Animals; D001682:Biological Availability; D001923:Brain Chemistry / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism; D004347:Drug Interactions; D005971:Glutamates / Q000494:pharmacology*; D006719:Homovanillic Acid / Q000378:metabolism; D007700:Kinetics; D007980:Levodopa / Q000097:blood / Q000378:metabolism*; D008297:Male; D008750:Methyldopa / Q000097:blood; D009043:Motor Activity / Q000187:drug effects; D010667:Phenylpyruvic Acids / Q000494:pharmacology*; D051381:Rats
D005971:Glutamates; D010667:Phenylpyruvic Acids; C019344:3,4-dihydroxyphenylpyruvic acid; D007980:Levodopa; D008750:Methyldopa; D004298:Dopamine; D006719:Homovanillic Acid