Alterations in rat liver microsomal enzymes following exposure to carbaryl and malathion in combination

Pesticides are a part of man's and animal's diet. The air we breathe and the water we drink also provide us with added measurable doses. Pesticides produce changes in -glucuronidase (-glu) content, which is highly concentrated in the liver. A study was conducted to examine the effect of carbaryl and malathion in combination on liver microsomal enzymes.In vitro studies which incubated rat serum, rat liver homogenate or purified -glu enzyme with 2 or 4 mM carbaryl and/or malathion had no effect on the -glu activity.Treatment with 50 mg/kg carbaryl daily for one week produced a significant 40% decrease in whole liver homogenate -glu activity. A single administration showed only a slight decrease through the 24-hr period examined. Rat liver subcellular fractionation studies revealed a significant decrease of 50% in microsomal -glu content one hr after a single administration of 50 mg/kg carbaryl. This decrease was correlated with a subsequent decrease in the microsomal -glu levels and was noted after daily treatment for one week with 50 mg/kg carbaryl.Incubation of 4 mM carbaryl with microsomal suspensions revealed a release of the microsomal -glu enzyme, whereas 4 mM malathion exerted an inhibition on the release of this enzyme. The combination of carbaryl and malathion (4/4 mM) produced an effect between that caused by either pesticide alone. This effect was not significantly different from the vehicle control until 30 min after the addition of the pesticide combination. To further exemplify an effect on the endoplasmic reticulum, it was observed that 25 mg/kg carbaryl, as well as 25/ 25 mg/kg carbaryl/malathion induced the UDP-glucuronyl transferase activity following daily treatment for seven days. These results revealed a decrease in microsomal -glu activity and calcium was correlated with their respective increases observed in the serum.