Effects of diethyldithiocarbamate on the catabolism of tyrosine in the rat brain.

500 mg/kg sodium diethyldithiocarbamate (DDC) and trace quantities of uniformly labelled 14C-tyrosine were administered simultaneously to male albino rats of Porton-Wistar strain of approximately 210 g body weight. Thirty minutes later total radioactivity, the concentration and the specific activity of free tyrosine were increased both in plasma and in the brain by 40% compared with rats untreated with DDC. The incorporation of 14C from 14C-tyrosine into the fraction corresponding to the elution of glutamine-glutamate from the amberlite resin column was 80% less in the brain 30 min after DDC. The exhalation of 14CO2 was depressed by 80% in the first hour after DDC. When 14C-tyrosine was given 3.5 h after DDC the only differences between experimental and control rats were the increased incorporation of 14C into the glutamine-glutamate and aspartate fractions and the increased exhalation of 14CO2 which became significiant in the third and fourth half hour periods after the injection of 14C-tyrosine. From the experiments it is concluded that DDC, an inhibitor of dopamine-beta-hydroxylase, also interferes with the major catabolic pathway of tyrosine.