US EPA

4120549 

Technical Report 

(Biolchemical mechanism of the toxicity of dithiocarbamate series fungicides: The inhibitory action on dopamine beta-hydroxylase activity.) 

Truhaut R, , JR; Guerinot F, , JR; Bohuon C, , JR 

1971 

HAPAB/71/02169 

Pharm 

2 

French 

HAPAB The effect of nabam (disodium ethylene bisdithiocarbamate) on dopamine beta-hydroxylase in vitro as well as on the metabolism of catecholamines in rats during acute intoxication were studied. Dopamine beta-hydroxylase was extracted from beef adrenal medulla (Levin et al., 1960). Dopamine chlorohydrate was used as the substrate in a medium containing 100 mcmoles potassium phosphate buffer, 10 mcmoles ATP, 10 mcmoles fumaric acid, 6 mcmoles ascorbic acid, 0.2 to 1 mcmoles dopamine chlorohydrate and 0.2 mg dopamine beta-hydroxylase. The mixture was incubated for 10 min at 37 C. Nabam was preincubated with the mixture for 1 min at 37 degrees prior to the introduction of dopamine. A chromatographic technique was used to detect the amount of noradrenaline formed. In subsequent studies, the amount of noradrenaline found was determined fluorometrically (Von Euler and Floding, 1955). In the in vivo experiments, Sprague-Dawley male rats weighing about 250 g were given a single i.p. injection containing 50, 100, 150 or 200 mg/kg nabam in aqueous solution and sacrificed 4 or 8 hr later. Dopamine and noradrenaline were determined by the modified techniques of MacGeer (1962) and Von Euler and Lishajko (1961), respectively. Nabam was shown to be a strong inhibitor in vitro of dopamine beta-hydroxylase, with total inhibition occurring at a concentration of 0.00000410 M. The in vivo experiments with rats showed that acute poisoning doses (50 to 400 mg/kg) of nabam were needed to produce even a slight decrease in the level of brain norepinephrine. 1971