TISSUE DISTRIBUTION OF COCAINE METHYL ESTERASE AND ETHYL TRANSFERASE ACTIVITIES - CORRELATION WITH CARBOXYLESTERASE PROTEIN

The tissue distribution of cocaine methyl esterase and ethanol-depende nt ethyl transferase activities was determined in the rat and compared to the tissue distribution of three distinct nonspecific hydrolases. Rates of formation of benzoylecgonine from cocaine and cocaethylene fr om ethanol and cocaine were measured in serum and tissue homogenate-su pernatants of the brain, heart, kidney, liver, lung and spleen. The ti ssue distribution of three nonspecific esterases, A, B and C, was defi ned by nondenaturing gel electrophoresis and measuring the hydrolysis of 4-methylumbelliferyl acetate in the gels. Immunoreactive protein wa s localized by using Western blot analysis with polyclonal rabbit anti human liver cocaine methyl esterase antibody after denaturing and nond enaturing gel electrophoresis. The rat liver, lung, kidney and heart e xhibited cocaine methyl esterase and ethyl transferase activities and immunoreactive protein. The brain had cocaine methyl esterase activity but no ethyl transferase activity; neither activity was found in seru m or spleen. The dominant immunoreactive bands in the liver, lung, kid ney and heart comigrated with the 59 kD band of purified human liver c ocaine methyl esterase. The rat liver, lung and kidney exhibited a ban d of nonspecific esterase activity that migrated with purified human l iver cocaine methyl esterase and rat hydrolase A. These observations s uggest that rat hydrolase A is similar to human cocaine methyl esteras e. The lack of straight forward correlation between cocaine methyl est erase activity and immunoreactive protein and nonspecific esterase act ivity suggests that more than one enzyme catalyzes the hydrolysis of c ocaine to benzoylecgonine in the rat.