Acute oral toxicity of aluminum phosphide in male albino rats (Wistar)

Melatonin reduces phosphine-induced lipid and DNA oxidation in vitro and in vivo in rat brain

Phosphine (PH(3)), a widely used pesticide, was found in our recent study to induce oxidative damage in the brain, liver and lung of rats. We also observed that melatonin significantly blocked this action. The present study focused on brain and the magnitude and mechanism of protection of PH(3)-induced oxidative damage by melatonin in vitro and in vivo. PH(3) in whole brain homogenate (3 mg protein/mL Tris-HCl pH 7.4 buffer) induced increasing lipid peroxidation [as malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA)] dependent on concentration (0.25-2 mM) and time (30-150 min), reaching a maximum level of 2.9-fold at 90 min after PH(3) at 1 mM. Elevation of MDA + 4-HDA levels by PH(3) at 1 mM was also observed in homogenates of cerebral cortex, cerebellum, hippocampus and hypothalamus examined individually. Melatonin at 0.1-2 mM progressively inhibited PH(3)-induced lipid peroxidation in brain and regions thereof. Additionally, PH(3) induced brain DNA oxidation in vitro and in vivo determined as 8-hydroxyguanosine (8-OH-dG). Melatonin at 1 mM significantly suppressed PH(3)-induced brain DNA oxidation in vitro. PH(3) at 4 mg/kg i.p. significantly elevated 8-OH-dG in frontal cortex and melatonin prevented it. PH(3) in vivo marginally lowered brain glutathione peroxidase activity and melatonin restored it completely. In contrast, PH(3) and melatonin both stimulated superoxide dismutase production. Brain glutathione (GSH) levels in PH(3)-treated rats were significantly reduced at 30 min and recovered gradually. It is concluded that melatonin, probably because of its free radical scavenging ability, confers marked protection against PH(3)-induced oxidative toxicity in brain.

Phosphine-induced oxidative damage in rats: attenuation by melatonin

Phosphine (PH(3)), from hydrolysis of aluminum, magnesium and zinc phosphide, is an insecticide and rodenticide. Earlier observations on PH(3)-poisoned insects, mammals and a mammalian cell line led to the proposed involvement of oxidative damage in the toxic mechanism. This investigation focused on PH(3)-induced oxidative damage in rats and antioxidants as candidate protective agents. Male Wistar rats were treated ip with PH(3) at 2 mg/kg. Thirty min later the brain, liver, and lung were analyzed for glutathione (GSH) levels and lipid peroxidation (as malondialdehyde and 4-hydroxyalkenals) and brain and lung for 8-hydroxydeoxyguanosine (8-OH-dGuo) in DNA. PH(3) caused a significant decrease in GSH concentration and elevation in lipid peroxidation in brain (36-42%), lung (32-38%) and liver (19-25%) and significant increase of 8-OH-dGuo in DNA of brain (70%) and liver (39%). Antioxidants administered ip 30 min before PH(3) were melatonin, vitamin C, and beta-carotene at 10, 30, and 6 mg/kg, respectively. The PH(3)-induced changes were significantly or completely blocked by melatonin while vitamin C and beta-carotene were less effective or inactive. These findings establish that PH(3) induces and melatonin protects against oxidative damage in the brain, lung and liver of rats and suggest the involvement of reactive oxygen species in the genotoxicity of PH(3).