Interaction of pyridostigmine and physical stress on antioxidant defense system in skeletal muscle of mice.

Pyridostigmine bromide (PB), a reversible anticholinesterase drug, had been used against possible nerve gas exposure during the Persian Gulf War. The Gulf War veterans used PB and they were under physical stress. This study investigated the delayed and interactive effects of pyridostigmine and physical stress on the antioxidant defense system in triceps muscle of mice. Male NIH Swiss mice were divided into four groups and treated as follows: sedentary control; pyridostigmine (1.2 mg kg(-1) p.o.); exercise; and PB plus exercise. Mice were exercised for 10 weeks, but PB was administered daily during the 5th and 6th weeks. Mice were sacrificed 24 h after the last treatments and the triceps muscle was isolated and analyzed. There was a significant increase in total superoxide dismutase (CuZn-SOD + Mn-SOD) activity (141% of control) with PB plus exercise, suggesting that any influx of superoxide anions was scavenged efficiently. The Mn-SOD enzyme protein levels were reduced significantly (63% of control) by PB plus exercise. Catalase enzyme protein levels were increased significantly by exercise (132% of control) as well as by PB plus exercise (139% of control). Glutathione levels were increased significantly by exercise alone (123% of control). Pyridostigmine bromide plus exercise significantly increased the malondialdehyde concentration (124% of control) in the triceps muscle, indicating an oxidative stress response of the combination. The data indicate that a combination of PB ingestion and exercise training significantly altered the antioxidant enzyme activities, enzyme protein levels and lipid peroxidation, leading to oxidative injury. Physical stress amplified the delayed effects of PB in the skeletal muscle of mice.