The properties of udp-glucuronyltransferase for cannabinoids in rat liver microsomes

Abstract

The glucuronidation of A9-tetrahydrocannabinol (A9-THC), cannabidiol (CBD) and cannabinol (CBN) in rat liver microsomes was studied. The enzyme activities for the can-nabinoids were 26.3 (A9-THC), 52.9 (CBD) and 104.8 (CBN) pmol/min/mg protein. The apparent Am values of UDP-glucuronyltransferase for the cannabinoids were 0.29 (A9-THC),0.18 (CBD) and 2.78 (CBN) mM, while Vmax were 40.3 (A9-THC), 104.9 (CBD) and 593.3 (CBN) pmol/min/mg protein. Following treatment of rats with 3-methylcholanthrene, the enzyme activities for A-THC, CBD and CBN were increased 132,43 and 1198%, respectively, whereas the corresponding increases in microsomes from phenobarbital-treated rats were 127,13 and 97%, respectively. The cannabinoid glucuronidation was activated 2 to 3 folds by the addition of UDP- N-acetylglucosamine, but not activated by the addition of Triton X-100 in vitro. The properties of cannabinoid UDP-glucuronyltransferase were discussed from the above results. © 1983, The Pharmaceutical Society of Japan. All rights reserved.