Biological Fate of ¹⁴C-L-DOPA in Mice

Abstract

¹⁴C-Catechols and other radioactive metabolites in the tissues and 6 hour-urine of mice given ¹⁴C-L-dopa orally were determined quantitatively.
The concentrations of total radioactivity and ¹⁴C-catechols in various tissues except the adrenal reached a peak at 20 minutes after administration and thereafter decreased gradually.
¹⁴C-Catechols in the adrenal kept high concentration until 6 hours after administration. The great part of ¹⁴C-catechols in the adrenal was found to be due to ¹⁴C-catecholamines. The percentage of ¹⁴C-cateeholamines in the brain was the highest among various tissues except the adrenal.
Unchanged ¹⁴C-L-dopa accounted for only a few percentages of the radioactivity in various tissues. Of the radioactivity excreted 6 hour-urine, 44% was homovanillic acid, 38% was conjugated metabolites, and 15.1% was catechols. The catechols consisted of adrenaline (3.2%), noradrenaline (4.1%), dihydroxyphenyl acetic acid (2.8%), dopa (1.75%) and dopamine (1.45%) . Whereas conjugates consisted of dopa (12.8%), homovanillic acid (6.1%), dopamine (5.6%), adrenaline (4.3%), dihydroxyphenyl acetic acid (2.2%), noradrenaline (2.7%) and unknown metabolites (3.9%) .