Transamination and other metabolic pathways of 3,4-dihydroxyphenylpyruvic acid in rats when simultaneously administered with L-dopa.
In the rat, 3,4-dihydroxyphenylpyruvic acid (DHPPA) was shown to be transaminated to L-dopa when administered orally concomitantly with L-[3H]dopa. As much as 40% of the serum L-dopa and brain dopamine was shown to be formed via transamination. Moreover, it was shown that DHPPA also caused a so-called L-dopa-sparing effect, i.e. more administered L-dopa reached the circulation and consequently more dopamine reached its target than after administration of L-dopa alone. This effect might be due to an inhibition of the deamination of L-[3H]dopa, since in this case the equilibrium of the transamination reaction will be forced into the L-dopa-forming direction. After administration of [14C]DHPPA alone and together with L-dopa, no differences in the absorption and distribution of radioactivity were found.
D000818:Animals; D001711:Biotransformation; D001923:Brain Chemistry; D004298:Dopamine / Q000378:metabolism; D007980:Levodopa / Q000378:metabolism*; D008297:Male; D010667:Phenylpyruvic Acids / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D010667:Phenylpyruvic Acids; C019344:3,4-dihydroxyphenylpyruvic acid; D007980:Levodopa; D004298:Dopamine