2005 年 51 巻 3 号 p. 369-375
The inhibitory effects of three major cannabinoids [Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN)] contained in marijuana, an abused drug, on progesterone 17α-hydroxylase activity in rat testis microsomes were investigated. Microsomal progesterone 17α-hydroxylase activity was significantly inhibited in the presence of more than 50 μM of Δ9-THC and CBN compared with control activity, and the IC50 values for Δ9-THC and CBN were estimated to be 42.8 and 32.9 μM, respectively. CBD showed less but significant inhibitory effects on 17α-hydroxylase activity at concentrations greater than 100 μM, and the IC50 value for the cannabinoid was estimated to be 290.9 μM. Kinetic analysis using double reciprocal plots showed that the type of inhibition by CBN was competitive, whereas that of Δ9-THC and CBD was the mixed type. These results suggest that the inhibition may be due to metabolic interactions between each cannabinoid and 17α-hydroxylase.