Biochemical changes in primary culture of skeletal muscle cells following dimethoate exposure

Abstract In order to investigate the cellular mechanism of muscular weakness in the Intermediate Myasthenia Syndrome (IMS) following acute organophosphate poisoning, we studied the cytotoxicity of dimethoate and its effects on the activity of acetylcholine esterase (AChE), Na + –K + -ATPase, succinate dehydrogenase (SDH), and Ca 2+ -ATPase in primary cultured skeletal muscle cells. The results showed that the activity of AChE was significantly inhibited in a dose and time-dependent manner when cells were exposed to dimethoate for 2 h, but the expression of heat-shock protein (HSP70) in muscle cells was significantly increased in a time-dependent manner following dimethoate exposure. Dimethoate can significantly increase the activity of Na + –K + -ATPase in the mitochondrial and cytoplasm fraction of muscle cells, and inhibit the activity of Ca 2+ -ATPase. This study suggests that the disruption of intracellular homeostasis and energy metabolism of the muscle cells may play a role in the etiology of IMS.