THE EFFECT OF METHYLMERCURY ON SKELETAL-MUSCLE IN THE RAT - A HISTOPATHOLOGICAL STUDY

Methylmercury (MeHg)-induced neurotoxicity includes skeletal muscle sy mptoms (extremity weakness and wasting, muscle cramp) in addition to a taxia and disturbances of sensory and visual function. The underlying mechanisms responsible for the skeletal muscle symptoms are still poor ly understood. In this study the effects of MeHg exposure on skeletal muscle were investigated in rats receiving orally administered MeHgCl at 5 mg/kg/day for 12 days. MeHg-treated rats gradually lost body weig ht and showed muscle weakness and wasting. Seven days after the last M eHg dose, MeHg levels in the skeletal muscle were as high as those in liver, kidney, or cerebrum. The obvious histopathological finding in s keletal muscle was a decrease in mitochondrial enzyme activity. These changes were more prominent in mitochondria-rich soleus muscle than in extensor digitorum longus muscle. Our findings confirm that MeHg expo sure disturbs mitochondrial energy metabolism in skeletal muscle. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.