AMELIORATIVE EFFECTS OF ASCORBIC ACID ON NEUROBEHAVIOURAL, HAEMATOLOGICAL AND BIOCHEMICAL CHANGES INDUCED BY SUB-CHRONIC LEAD EXPOSURE IN WISTAR RATS

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Date
2010-02
Authors
OLALEKAN, OLADIPO OLUSOLA
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Abstract
ABSTRACT Experiments were performed with the aim of evaluating the effects of sub-chronic exposure to lead and the protective role of ascorbic acid on toxic changes in Wistar rats. Forty adult Wistar rats (20 males and 20 females) divided into 4 groups of 10 animals each (5 males and 5 females in each group) served as subjects for this study. Rats in group I were given distilled water only. Rats in group II were exposed to lead acetate only at 200 mg/kg, while those in group III were pre-treated with ascorbic acid only at a dose of 100 mg/kg. Rats in group IV were pre-treated with ascorbic acid at a dose of 100 mg/kg before being administered with lead acetate 30 minutes later. The regimens were administered orally once daily for a period of six weeks. The effects of the different treatments on body weight change, open-field activities, sensorimotor reflexes and cognition were evaluated in the rats. Packed cell volume (PCV), haemoglobin concentration (Hb), total erythrocyte count (RBC), total leucocyte count, differential leucocyte count and erythrocyte osmotic fragility (EOF) test were determined using standard methods. Total protein, albumin and globulin concentrations, and activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and creatine kinase (CK) were measured using standard methods. Lipid peroxidation was determined by measuring the thiobarbituric acid reactive substance; malondialdehyde (MDA) in the brain of the rats. Serum thyroid hormone levels were also determined using radioimmunoassay. The results demonstrated that sub-chronic exposure to lead in rats had no effect on body weight change. There was no significant (P > 0.05) change in sensorimotor reflexes of the rats. Rats in the lead-treated group showed an increased anxiety compared to the control and those pre-treated with ascorbic acid. Rats in the lead group also showed a significant (P < 0.05) decline in cognitive function compared to those in the control and ascorbic acid-pretreated groups. The haematology showed significant (P < 0.05) reductions in PCV, Hb and RBC in the lead9 treated group compared to the control rats. Lead also caused leucocytosis due to a significantly (P < 0.05) higher neutrophil/lymphocyte ratio. There was slight but insignificant increase in EOF in rats exposed to lead, compared with the control groups. A significant (P < 0.05) decrease in AST, LDH, CK and a slight increase in MDA was observed in the lead treated rats compared to the control groups. There were tissue changes in the lead-treated group compared with the control and the ascorbic acid pre-treated groups. The study demonstrated that increased lipid peroxidation, low thyroid indices and decreased CK activity may be involved in the mechanism of neurobehavioural and cognitive impairments by lead. In conclusion, the study showed that sub-chronic exposure to lead induced anxiogenic effects, cognitive, haematological, biochemical and pathological changes in rats, ameliorated by pretreatment with ascorbic acid. It is, therefore, recommended that individuals, who are constantly exposed to lead, should be pretreated with vitamin
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DEPARTMENT OF VETERINARY PHYSIOLOGY AND PHARMACOLOGY AHMADU BELLO UNIVERSITY, ZARIA NIGERIA.
Keywords
PARTIAL,, FULFILLMENT,, REQUIREMENTS,, AWARD,, DEGREE,, MASTER,, SCIENCE,, VETERINARY,, TOXICOLOGY
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