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.