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The present study investigated the protective effects of zinc in attenuating the altered activities of drug metabolizing enzymes in the livers of rats intoxicated with chlorpyrifos. Male Sprague-Dawley rats received oral chlorpyrifos treatment (at a dose level of 13.5 mg/kg body weight in corn oil every alternate day), zinc supplementation alone (at a dose level of 227 mg/l in drinking water), or combined chlorpyrifos plus zinc treatments for a total duration of 8 weeks. The effects of different treatments were studied on the specific activities of various drug metabolizing enzymes including cytochrome P(450), cytochrome b(5), NADPH cytochrome-c-reductase, NADH cytochrome-c-reductase, aminopyrene-N-demethylase (APD) and aromatic hydrocarbon hydroxylase (AHH). Additionally, serum zinc levels were also determined in each of the treatment groups at the end of the study. Chlorpyrifos treatment resulted in a significant decrease in the serum zinc concentrations. Analogous to these changes, we observed significant depression in the activities of majority of the drug metabolizing enzymes investigated in the present study, except for AHH, where the decrease in enzyme activity was not statistically significant. However, zinc treatment to chlorpyrifos treated animals effectively restored the depressed serum zinc levels to within normal limits. Similarly, co-administration of zinc to chlorpyrifos intoxicated animals normalized the enzymatic activities of cytochrome P(450), NADPH cytochrome-c-reductase and NADH cytochrome-c-reductase within normal range. Collectively, these findings suggest that zinc plays an important role in regulating the hepatic activities of drug metabolizing enzymes in chlorpyrifos intoxicated animals, although it remains to be determined whether such protective effects of zinc are regulated directly, or through some indirect mechanism.

The present study determined the protective potential of zinc in attenuating the toxicity induced by chlorpyrifos in rat blood. Male Sparque Dawley (SD) rats received either oral chlorpyrifos (13.5 mg/kg body weight) treatment every alternate day, zinc alone (227 mg/l in drinking water) or combined chlorpyrifos plus zinc treatment for a total duration of 8 weeks. The effects of different treatments were studied on various parameters in rat blood including haemoglobin (Hb) levels, total leukocyte count (TLC), differential leukocyte count (DLC), zinc protoporphyrins (ZPP), serum trace elemental concentrations and Scanning Electron Microscopic (SEM) observation of the blood cells. Chlorpyrifos treatment to normal control animals resulted in a significant decrease in TLC and ZPP concentration after 4 and 8 weeks. Chlorpyrifos treated animals also showed significant neutrophilia and lymphopenia after 8 weeks of toxicity. In addition, a significant decrease in serum zinc and iron concentrations were observed following chlorpyrifos intoxication, however, these animals responded with increased serum copper levels following the toxic treatment with this organophosphate. SEM studies of the red blood cells from chlorpyrifos treated animals indicated marked alterations in the topographical morphology of the various cell types, with the prominent feature being common aniscocytosis of the erythrocytes. Oral zinc treatment to the chlorpyrifos treated animals significantly improved the total leukocyte, neutrophil and lymphocyte counts, as well as the otherwise reduced concentrations of ZPP and the levels of various serum trace elements. Protective effects of zinc were also evident in the electron microscopic observations where most blood cell types depicted reverted to a close to the normal appearance. Based upon these data, the present study is first of its kind and suggests that zinc treatment considerably attenuates chlorpyrifos induced toxicity induced in restoring the altered hematological indices and morphological changes.

The present study was conducted to evaluate the adverse effects of chlorpyrifos on the key enzymes of carbohydrate metabolism in liver, and also to assess the role of zinc under these toxic conditions. Male Sprague-Dawley (SD) rats received either oral chlorpyrifos treatment (13.5 mg/kg body weight in corn oil) every alternate day, zinc alone (227 mg/l in drinking water), or combined chlorpyrifos and zinc treatments for a total duration of 8 weeks. The effects of different treatment regimens were studied on various enzymes of carbohydrate metabolism in the rat livers, which included hexokinase, glucose-6-phosphatase, fructose-1,6-diphosphatase, glycogen phosphorylase, succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and the levels of glycogen. In vitro uptake of (14)C-D-glucose was also assessed in liver slices after similar treatments. Chlorpyrifos intoxication resulted in a significant increase in the activities of glucose-6-phosphatase and glycogen phosphorylase, whereas, it caused a significant inhibition in the levels of hexokinase, SDH, LDH and glycogen content. However, zinc treatment to chlorpyrifos-intoxicated animals was able to normalize the activities of most of these enzymes to either close to, or within normal limits. Chlorpyrifos intoxication demonstrated significantly inhibited (14)C-D-glucose uptake in liver slices, which again was reversed to normal limits following simultaneous zinc treatment. Levels of metallothionein were also found to be depressed in chlorpyrifos-treated animals, but tended to increase significantly on co-administration of zinc to chlorpyrifos-treated group. Hence, the present study clearly suggests that zinc plays an important role in regulating the hepatic activities of the enzymes involved in carbohydrate metabolism under conditions of chlorpyrifos toxicity.

The present study investigated the hepatoprotective role of zinc in attenuating the toxicity induced by chlorpyrifos in rat liver. Male Sprague-Dawley (SD) rats received either oral chlorpyrifos (13.5mg/kg body weight), zinc alone (227mg/l in drinking water) or combined chlorpyrifos plus zinc treatment for a total duration of 8 weeks. The effects of these treatments were studied on various parameters in rat liver, including lipid peroxidation, antioxidant enzymes, levels of metallothionein (MT) and hepatic histoarchitecture. Chlorpyrifos treatment resulted in a significant increase in hepatic lipid peroxidation and activities of superoxide dismutase (SOD), glutathione peroxidase (G-Px) and glutathione reductase (GR). On the contrary, chlorpyrifos intoxication caused a significant inhibition in the levels of reduced glutathione (GSH), catalase (CAT) and glutathione-S-transferase (GST) activities. However, zinc treatment to chlorpyrifos-intoxicated animals normalized the otherwise raised levels of lipid peroxidation to within normal limits. Moreover, zinc treatment to these animals resulted in an elevation in the levels of GSH, catalase and GST, as well as a significant decrease in the levels of SOD. Levels of MT were also found to be depressed in chlorpyrifos-treated animals, but tended to increase following co-administration of zinc. Additionally, chlorpyrifos-treated animals demonstrated increased vacuolization, necrosis and ballooning of the hepatocytes and dilatation of sinusoids as well as increase in the number of binucleated cells. However, zinc administration to chlorpyrifos-treated animals resulted in overall improvement in the hepatic histoarchitecture, emphasizing the protective potential of zinc. Hence, the present study suggests the protective potential of zinc in alleviating the hepatic toxicity induced by chlorpyrifos.