Influence of mercury on uptake of [ 3h]dopamine and [ 3h]norepinephrine by rat brain synaptosomes

Abstract

Mercuric compounds have been shown to alter several membrane-bound enzymes and associated receptor activities. The present studies were initiated to investigate the in vitro effects of mercuric chloride (HgCl 2) and methylmercury chloride (CH 3HgCl) on the uptake of [ 3H]dopamine ( 3HDA), [ 3H]norepinephrine ( 3HNE), and Na +, K +-ATPase in rat brain synaptosomes. Brain synaptosomes were prepared by the ficoll-sucrose gradient method from normal, adult male Sprague-Dawley rats, weighing approx. 200 g. The effect of mercury on Na +, K + -ATPase was determined by using a coupled enzymatic method. Uptake of DA and NE by brain synaptosomes was determined by filtration in the presence and absence of 0–30 μM HgCl 2 and 0–100 μM CH 3HgCl. A parallel inhibition in the synaptosomal uptake of 3HDA and 3HNE, and the activity of the synaptosomal membrane Na +, K +-ATPase, was observed in both mercuric chloride and methylmercury treatments. The mercury compounds also significantly inhibited the mitochondrial ATPase (Mg 2+-oligomycin-sensitive ATPase). The inhibitory influences of the toxins were concentration-dependent. The results suggest that the mercury compound mediated decrease in DA and NE uptake in brain synaptosomes may be related to the inhibition of Na +, K +-ATPase by the same toxins.