DIVERGENT EFFECTS OF CLASSICAL INDUCERS ON RAT PLASMA AND MICROSOMAL FRACTION PARAOXONASE AND ARYLESTERASE

The effects of three different enzyme-inducing agents (phenobarbital, 3-methylcholanthrene and rifampicin) on plasma and liver microsomal fr action paraoxonase and arylesterase were studied in rats. Although phe nobarbital and 3-methylcholanthrene each increased the esterase activi ties in microsomal fraction, only 3-methylcholanthrene was capable to increase them in plasma. By contrast, the administration of rifampicin decreased both enzyme activities in liver and plasma. The results ind icate that at least there exists two esterase activities in rat liver microsomes which hydrolyse both paraoxon and phenylacetate, but only o ne of them is released into the blood. (C) 1997 Elsevier Science B.V.