Melatonin protects against lead acetate induced oxidative stress-mediated changes in morphology and metabolic status in rat red blood cells: a flow cytometric and biochemical analysis

ABSTRACT Background: Lead is an abundantly occurring heavy metal known to be toxic in higher quantities for humans and other animals. Moreover, lead exposure has previously been shown to cause damage to red blood cell. However, a detailed study with a plausible mechanism is still lacking. The pineal hormone, melatonin, is well known for its antioxidant and free radical scavenging properties. Thus, we examined the effect of melatonin pre-treatment on lead acetate-induced toxicity in rat RBCs in vivo as well as in vitro and tried to find out the mechanism behind such protection. Main methods: Rats were injected intra-peritoneally with lead acetate (15mg/kg/day) for seven consecutive days in presence/ absence of melatonin (10mg/kg body weight). RBCs isolated from whole blood were haemolysed and was used for measuring changes in biochemical parameters and altered red blood cell morphology. Results & Discussion: Rats injected intra-peritoneally with lead acetate (15mg/kg/day) for seven days exhibited an altered status of lipid peroxidation level, reduced glutathione content, protein carbonyl and oxidized glutathione levels along with inhibition of superoxide dismutase and catalase activities in RBCs indicating generation of oxidative stress. Data obtained using light microscopy, scanning electron microscopy and flow cytometry indicate deterioration of RBC morphology along with marked alterations in granularity. Atomic absorption spectrophotometric analysis revealed lead accumulation and reduction in iron and zinc levels along with decreased carbonic anhydrase and met haemoglobin reductase activities in RBCs isolated from lead acetate-treated rats. An increase in osmotic fragility and marked changes in the activities of the glutathione metabolising enzymes, hexokinase, glucose-6-phosphate dehydrogenase, aldolase, lactate dehydrogenase and acetylcholine esterase in RBC were also observed following lead acetate treatment. Rats pre-treated with melatonin (10mg/kg body weight) displayed restoration of these altered activities, suggesting its ameliorative action against lead acetate toxicity. Additionally, in vitro studies indicated that lead acetate-induced alterations of RBC enzyme activities are time and concentration-dependent and when co-incubated with melatonin, these changes were restored. Conclusion: The present study demonstrates the potential ability of melatonin to provide protection against lead acetate-induced injury to RBCs through its antioxidant properties in addition to removal of non-competitive inhibition of some of the enzymes