**6. Mechanism of action**

The exact mechanism of action of aluminum phosphide poisoning is still unknown, however an initial survey on different animals showed non-competitive cytochrome oxidase binding by phosphine, changes valences of haeme component of haemoglobin.Other than later articles, distinguished significant inhibition of catalase goes to hydrogen peroxide agglomeration (Price, et al, 1982), Extra-mitochondrial release of hydrogen peroxide and oxygen free radicals (Bolter & Chertuka, 1989), leading to lipid peroxidation and protein denaturation of cell membrane are reported in more recent studies (Chug, et al, 1969). Also, aluminum and phosphine (Potter, et al, 1993; Al-Azzawi, et al, 1990), inhibit cholinesterases activity . Al-Azzawi showed in vitro exposure to phosphine lead to reducing human serum cholinesterase activity; in addition he showed the amount of the inhibition is related to the duration and concentration of phosphine (Al-Azzawi, et al, 1990). On the other hand, other studies declared there is no erythrocyte cholinesterase activity reduction in humans after accidental phosphine inhalation (Heyndrickx, et al, 1976; Wilson, et al, 1980).
