The effect of colupulone (a hops β-acid) on hepatic cytochrome P-450 enzymatic activity in the rat

Colupulone, a component of hops, was examined for its ability to alter rat hepatic cytochrome P-450 enzymatic activity, expression of hepatic cytochrome P-450 mRNA, and in vitro promutagen activation. Colupulone was fed to male Sprague-Dawley rats for 5 days at 0.36% in the modified AIN 76 diet. Three cytochrome P-450 enzymatic activities were measured, and the corresponding steady-state mRNA levels were examined by Northern blot hybridization. Colupulone increased cytochrome P450IIB and P450IIIA steady-state mRNA levels. In vitro promutagen activation was measured in the Ames assay using liver homogenates from each treatment group. Colupulone treatment did not alter the ex vivo cytochrome P-450-mediated activation of aflatoxin B₁ or benzo[a]pyrene to their mutagenic forms. The effect of long-term colupulone administration on in vivo cytochrome P-450 enzymatic activity remains to be determined.